Write image service docs

src/web/docusaurus/docs/api-services/image.md

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+---
+sidebar_position: 4
+---
+
+# Image Service
+
+## Overview
+
+The image service provides the images used in the hero banner found in the Telescope web page.
+
+## API endpoints
+
+### Get a random image or get a specific image by its name
+
+```
+GET /
+```
+
+#### Parameters
+
+| Name  | Type             | In    | Description                                                                                                                           |
+| ----- | ---------------- | ----- | ------------------------------------------------------------------------------------------------------------------------------------- |
+| image | string OR number | path  | _Optional_. The exact name of the image if the value is a string, otherwise an index of the image (value is a number).                |
+| w     | number           | query | _Optional_. The width of the image. It can be between 40 and 2000, inclusive. Defaults to 800.                                        |
+| h     | number           | query | _Optional_. The height of the image. It can be between 40 and 3000, inclusive. Defaults to the height of the image when width is 800. |
+| t     | string           | query | _Optional_. The type of image to render. It may be one of the following: `jpeg`, `jpg`, `png`, `webp`. Defaults to `jpeg`.            |
+
+#### Code Samples
+
+##### Shell
+
+```bash
+curl http://localhost/v1/image
+```
+
+```bash
+curl http://localhost/v1/image/0
+```
+
+```bash
+curl http://localhost/v1/image/default.jpg
+```
+
+##### JavaScript
+
+- With `fetch`
+
+```js
+fetch('http://localhost/v1/image/');
+```
+
+```js
+fetch('http://localhost/v1/image/0');
+```
+
+```js
+fetch('http://localhost/v1/image/default.jpg');
+```
+
+#### Responses
+
+##### Successful response
+
+```
+Status: 200 OK
+```
+
+The body is an image file, with a specific image format ([`WebP`](https://en.wikipedia.org/wiki/WebP)).
+
+##### Bad Request
+
+```
+Status: 400 Bad Request
+```
+
+This could be due to the `image` argument trying to access other parts of the filesystem by going to other directories (e.g. `../access/somewhere/dangerous.jpg`).
+
+##### Not Found
+
+```
+Status: 404 Not Found
+```
+
+This occurs when a given `image` parameter is for an image that does not actually exist.
+
+##### Internal Server Error
+
+```
+Status: 500 Internal Server Error
+```
+
+This error is an unexpected one, and a specific reason for the error to occur cannot be given.
+
+### Get a gallery of images
+
+```
+GET /gallery
+```
+
+#### Code Samples
+
+##### Shell
+
+```bash
+curl http://localhost/v1/image/gallery
+```
+
+##### JavaScript
+
+- With `fetch`
+
+```js
+fetch('http://localhost/v1/image/gallery');
+```
+
+#### Responses
+
+##### Successful response
+
+```
+Status: 200 OK
+```
+
+The body is an HTML page with all of the images available enlisted.