docs: Add contribution guide

Author: slusarz

docs/contributing.md

@@ -0,0 +1,63 @@
+---
+layout: doc
+title: Contributing
+order: 60
+---
+
+# Contributing to the Documentation
+
+There are several ways you can contribute to improving the Dovecot
+documentation.
+
+## Submitting Fixes and Improvements
+
+If you are familiar with Git and [GitHub](https://github.com/), you can
+submit your changes directly to the documentation repository.
+
+1. **Fork the repository:** Start by creating a fork of the official
+   [Dovecot documentation repository](https://github.com/dovecot/documentation/)
+   on GitHub.
+2. **Clone your fork:** Clone your newly created fork to your local machine:
+   ```shell
+   git clone https://github.com/YOUR_USERNAME/documentation.git
+   cd documentation
+   ```
+3. **Create a new branch:** Create a new branch for your changes. Choose a
+   descriptive name for your branch.
+   ```shell
+   git checkout -b my-awesome-fix
+   ```
+4. **Make your changes:** Edit the documentation files as needed.
+5. **Commit your changes:** Once you are happy with your changes, commit
+   them with a descriptive commit message. The commit message should be in
+   the format `docs: A brief summary of the change`.
+
+   The commit message should use imperative language ("Fix", "Change", "Add"),
+   not past-tense ("Fixed", "Changed", "Added"). Use a single prefix term
+   that describes the area of the documentation the commit affects (e.g.,
+   "settings", "fts").
+   ```shell
+   git commit -am "installation: Fix a typo in the installation guide"
+   ```
+6. **Push your changes:** Push your changes to your fork on GitHub.
+   ```shell
+   git push origin my-awesome-fix
+   ```
+7. **Create a Merge Request:** After pushing your commit, you should see a
+   GitHub link to create a merge request in the Git output contents. Click
+   on this link and complete the form to submit the merge request to the
+   official Dovecot repository. (If you don't see the link, go to your
+   personal fork of the documentation project on GitHub to find the
+   submission link.)
+
+## I Don't Know How to Code!
+
+Even if you're not comfortable with Git and GitHub, you can still contribute to the documentation. If you find a typo, a factual error, or have a suggestion for improvement, you can submit an issue to the [GitHub issue tracker](https://github.com/dovecot/documentation/issues).
+
+When submitting an issue, please include the following information:
+
+*   **The URL of the page** where you found the issue.
+*   **A description of the issue.** Be as specific as possible. For example, instead of saying "the documentation is confusing", say "in the section on XYZ, the first paragraph is unclear because...".
+*   **A suggestion for how to fix the issue.** If you have an idea for how to improve the documentation, please share it!
+
+The core developers will review your suggestion and incorporate it into the documentation if they agree that it's a good idea.