Documentation: Add block submission guidelines. (#23545)

* Rough document outline.

* A few updates.

* Update categories.

* Lowercase the categories.

* Fix embed category.

* Prefer 'block editor' to 'gutenberg'.

* Includes example data.

* Change sentence and capital case 'block editor'.

* update the intro sentence.

* Fix formatting.

* Fix the submit sections.

* Remove empty lines.

* Use more contextual link text

* Update block.json description

* update anchor link for keywords

* Replace paragraphs based on feedback.

* Update block directory references to be capital case.

* Update example copy.

* Update copy that points to example block.json.

* Update again.

* Update last property.

* Change example callout.

Co-authored-by: Kelly Dwan <ryelle@users.noreply.github.com>
Co-authored-by: Jeffrey Paul <jeffpaul@hotmail.com>

docs/designers-developers/developers/tutorials/create-block/submitting-to-block-directory.md

@@ -0,0 +1,101 @@
+# Share your Block with the World
+
+So you've created an awesome block? Care to share?
+
+**Contents**:
+1. Help users understand your block
+2. Analyze your plugin
+3. Zip & Submit
+
+## Step 1: Help users understand your block
+
+It is important to the Block Directory and our end users to provide easy to understand information on how your block was created.
+
+**Guidelines**:
+
+- Name your block based on what it does
+- Clearly describe your block
+- Add Keywords for all contexts
+- Choose the right category
+
+### Name your block based on what it does
+
+Users typically search the Block Directory within the Block Editor and do so in the context of a task. For example, when building their post, a user may search the Block Directory for an “image gallery”. Naming your block accordingly will help the Block Directory surface it when it's needed.
+
+**Not So Good**: WebTeam5 Image Works
+**Good**: Responsive Image Slider by WebTeam5
+
+**Question: What happens when there are multiple blocks with similar names?**
+Try your best to make your block's name functional and unique to make it stand out. Look for applicable synonyms or include a prefix if necessary.
+
+### Clearly describe your block
+
+The description really helps to communicate what your block does.The quicker a user understands how your block will help them, the more likely it is a user will use your block. Users will be reading your block's description within the Block Editor where space can be limited. Try to keep it short and concise.
+
+**Not So Good**: The best way to show images on your website using jQuery and CSS.
+**Good**: A responsive image gallery block. 
+
+**Tip**: It’s not about marketing your block, in fact we want to avoid marketing in blocks. You can read more about it in the [plugin guidelines]. Stick to being as clear as you can. The Block Directory will provide metrics to let users know how awesome your block is!
+
+### Add Keywords for broader context
+
+Keywords add extra context to your block and make it more likely to be found in the inserter. 
+
+Examples for an Image Slider block:
+- slider
+- carousel
+- gallery
+
+[Read more about keywords.](https://github.com/WordPress/gutenberg/blob/master/docs/rfc/block-registration.md#keywords)
+
+### Choose the right category
+
+The Block Editor allows you to indicate the category your block belongs in, making it easier for users to locate your block in the menu.
+
+**Possible Values**:
+- text
+- media
+- design
+- widgets
+- embed
+
+[Read more about categories.](https://github.com/WordPress/gutenberg/blob/master/docs/rfc/block-registration.md#category)
+
+Wondering where to input all this information? Read the next section :)
+
+## Step 2: Analyze your plugin
+Each block in your plugin should have a corresponding `block.json` file. This file provides the Block Directory important information about your block. Along with being the place to store contextual information about your block like the: `name`, `description`, `keywords` and `category`, the `block.json` file stores the location of your block’s files.
+
+Block plugins submitted to the Block Directory can contain mutliple blocks only if they are children of a single parent/ancestor. There should only be one main block. For example, a list block can contain list-item blocks. Children blocks must set the `parent` property in their `block.json` file.
+
+Double check that the following is true for your block:
+
+- `editorScript` is pointing to the JavaScript bundle that includes all the code used in the **editor**.
+- `editorStyle` is pointing to the CSS bundle that includes all the css used in the **editor**.
+- `script` is pointing to the JavaScript bundle that includes all the code used on the **website**.
+- `style` is pointing to the CSS bundle that includes all the code used on the **website**.
+
+We encourage the separation of code by using both editorScript/editorStyle and script/style files listed in your block.json to keep the backend and frontend interfaces running smoothly. Even though only one file is required.
+
+Here is an example of a basic block.json file.
+
+```json
+{
+  "name": "plugin-slug/image-slider",
+  "title": "Responsive Image Slider",
+  "description": "A responsive and easy to use image gallery block.",
+  "keywords": [ "slider", "carousel", "gallery" ],
+  "category": "media",
+  "editorScript": "file:./dist/editor.js",
+}
+```
+
+The `block.json` file also contains other important properties. Take a look at an [example block.json](https://github.com/WordPress/gutenberg/blob/master/docs/rfc/block-registration.md#registering-a-block-type) for additional properties to be included in the block.json file.
+
+
+## Step 3: Zip & Submit
+
+The community is thankful for your contribution. It is time to submit your plugin.
+
+Go through [the block guidelines](https://github.com/WordPress/wporg-plugin-guidelines/blob/block-guidelines/blocks.md). Create a zip file of your block and go to the [block plugin validator](https://wordpress.org/plugins/developers/block-plugin-validator/) and upload your plugin.
+