docs: add contribution guide (#57)

* docs: add contribution guide

* docs: link contribution guide in readme

* Apply suggestions from code review

Co-authored-by: Allan <al@ayz.ai>

* docs: remove excess msrv section

Co-authored-by: Allan <al@ayz.ai>

CONTIRBUTING.md

@@ -0,0 +1,99 @@
+# Contributing to _dotenvy_
+
+**Thank you very much for considering to contribute to this project!**
+
+We welcome any form of contribution, including:
+
+- reporting or fixing bugs
+- requesting or adding features
+- doc changes (including spelling/grammar corrections)
+- adding examples
+- asking for help, sharing ideas
+
+**Note**: Before making a large change, it is a good idea to open an issue
+describing the change to solicit feedback and guidance. This will increase the
+likelihood of the PR getting merged and help avoid multiple people writing the
+same solution.
+
+This guide will help you get started. Do not let this guide intimidate you. It
+should be considered a map to help you navigate the process.
+
+## Conduct
+
+The `dotenvy` project adheres to the [Rust Code of
+Conduct](https://www.rust-lang.org/policies/code-of-conduct).
+
+## Issues
+
+Please feel free to open new [issues](https://github.com/allan2/dotenvy/issues),
+or comment on existing ones. If you would like to attempt
+to implement a change, you can ask for help or guidance on solving a problem, or
+just let us know you are working on it.
+
+A maintainer will mark the issue as assigned to you to avoid other people
+unknowingly working on the same thing. If you would like to work on an assigned issue that has not been updated in a while, just ask to have it reassigned to you.
+
+This project sometimes has longer form
+[discussions](https://github.com/allan2/dotenvy/discussions). Feel free to
+comment on existing threads or open your own.
+
+## Pull Requests
+
+Pull Requests are the way concrete changes are made to the code, documentation,
+and dependencies in the dotenvy repository.
+
+Even tiny PRs, like a one character change to fix a typo in the docs, are greatly appreciated. Before making a large change, it is recommended to first open an issue describing the change as to solicit
+feedback and guidance. This will increase the likelihood of the PR getting
+merged.
+
+### Tests
+
+If you are modifying the code, make sure all tests pass. If you are adding new functionality, please add related tests.
+
+### Discuss and update
+
+If you receive feedback on your PR, please don't be discouraged. It's just part of the process to ensure that changes to the project are correct and necessary.
+
+Any community member can review a PR.
+
+#### Commit Squashing
+
+There is no need to squash your commits manually. PRs are usually squash merged anyway.
+
+### CI
+
+Please ensure that your PR passes the CI checks:
+
+- all tests pass on stable and [MSRV]
+- no [clippy](https://github.com/rust-lang/rust-clippy) warnings or errors
+- formatted with [Rustfmt](https://github.com/rust-lang/rustfmt)
+- [Rustdoc](https://doc.rust-lang.org/rustdoc/write-documentation/linking-to-items-by-name.html)
+  links work
+
+#### Add an entry to the changelog
+
+If your contribution changes the behavior of dotenvy, please update the
+[`CHANGELOG.md`](CHANGELOG.md) file and describe your changes. This makes the
+release process much easier and therefore helps to get your changes into a new
+dotenvy release faster.
+
+The top of the `CHANGELOG` contains an **Unreleased** section with a few
+subsections (Added, Changed, etc) Please add your entry to the subsection
+that best describes your change. If a relevant subsection does not yet exist, please
+create it.
+
+Entries follow this format:
+
+```md
+### Changed
+
+- Short description of what has been changed ([PR #123](pull.request.url)) by [username](github.profile.url)
+- [**BREAKING**] Please prefix any breaking changes
+```
+
+Here, `#123` is the number of your pull request.
+
+**NOTE**: It is a good idea to push the
+changelog update to your branch after opening the PR. That way you can copy the number and link.
+
+[MSRV]: README.md#minimum-supported-rust-version

README.md

@@ -68,8 +68,15 @@ It also adds:
 
 For a full list of changes, refer to the [changelog](./CHANGELOG.md).
 
+## Contributing
+
+Thank you very much for considering to contribute to this project! See
+[CONTRIBUTING.md](./CONTRIBUTING.md) for details.
+
+**Note**: Before you take the time to open a pull request, please open an issue first.
+
 ## The legend
 
 Legend has it that the Lost Maintainer will return, merging changes from `dotenvy` into `dotenv` with such thrust that all `Cargo.toml`s will lose one keystroke. Only then shall the Rust dotenv crateverse be united in true harmony.
 
-Until then, this repo dutifully carries on the dotenv torch. It is actively maintained. Contributions and PRs are very welcome!
+Until then, this repo dutifully carries on the dotenv torch. It is actively maintained.