[website] Add "Contribute Documentation" for community usage (#694)

Author: MehulBatra

website/community/how-to-contribute/contribute-docs.md

@@ -21,5 +21,152 @@ sidebar_position: 1
 
 # Contribute Documentation
 
-TODO
+The Fluss website serves as the primary interface between the project and its community, with several key purposes:
 
+* Introducing Fluss as a streaming storage solution for real-time analytics
+* Providing technical documentation for users and developers
+* Facilitating downloads and deployment guidance
+* Fostering community engagement and contributions
+* Showcasing Fluss features, use cases, and roadmap
+
+This website is built with Docusaurus, a modern static website generator optimized for documentation. For advanced features and tools, visit the [official Docusaurus documentation](https://docusaurus.io/).
+
+This guide will walk you through the process of contributing to the Fluss documentation, from setting up your environment to submitting your changes.
+
+## Build Documentation
+
+### Fork and Clone
+Fork the [Fluss repository](https://github.com/alibaba/fluss)
+    
+``` bash
+git clone https://github.com/<your-username>/fluss.git
+cd fluss
+```
+
+### Create a Branch
+```bash
+git checkout -b feature-branch-name
+```
+
+### Install Dependencies
+```bash
+cd website
+npm install
+```
+
+### Directory Structure
+The Fluss documentation is organized as follows:
+```
+fluss/website/
+├── docs/                    # Main documentation (current version)
+│   ├── intro.md
+│   ├── concepts/
+│   ├── quickstart/
+│   └── ...
+├── blog/                    # Release and feature blogs (not versioned)
+├── community/               # Community content (not versioned)
+├── static/                  # Static assets
+│   └── img/                 # Images for documentation
+├── versioned_docs/          # Previous versions of documentation
+│   ├── version-0.6/
+│   └── version-0.5/
+├── versioned_sidebars/      # Sidebar configurations for different versions
+├── src/                     # Source files for the website
+│   └── plugins/             # Custom plugins including version replacement
+├── build_versioned_docs.sh  # Script for building versioned docs
+├── docusaurus.config.ts     # Main configuration for Docusaurus website
+├── sidebars.ts              # Sidebar configuration
+└── package.json             # Node.js dependencies and scripts
+```
+
+### Validation (including versioned docs)
+- Edit or create Markdown files in the appropriate directories
+- Generate versioned docs (simulates what CI does)
+```bash
+./build_versioned_docs.sh
+```
+- Then build the complete site which checks broken links
+``` bash
+npm run build -- --no-minify
+```
+  
+### Preview Changes
+- Start the local development server to preview changes
+```bash
+npm run start
+```
+- View your changes at [http://localhost:3000/fluss-docs/](http://localhost:3000/fluss-docs/)
+
+## Versioned Documentation
+- Only content in `website/docs/* `is versioned
+- Each version corresponds to a branch (e.g., release-0.5, release-0.6)
+- Fixes for `website/docs/*` documentation related to old versions should be backported to their corresponding release-x.y branches
+- The main branch contains the latest (unreleased) documentation
+- Other pages (community, roadmap) are only maintained in the main branch
+
+### Updating Existing Versions
+- Checkout the corresponding release branch
+``` bash
+git checkout release-0.5
+```
+- Make changes to files in `website/docs/`
+- Create a pull request to that specific release branch
+
+### Version Expressions
+Fluss documentation uses placeholder variables that are automatically replaced during the build process. Note that these variables are only available for documentation under `website/docs/*`.
+- `$FLUSS_VERSION$`: Expands to the full version (e.g., "0.6.0")
+- `$FLUSS_VERSION_SHORT$`: Expands to the short version (e.g., "0.6")
+
+For example, to link to a specific version of Fluss binary:
+
+```bash
+tar -xzf fluss-$FLUSS_VERSION$-bin.tgz
+```
+
+The above code block will be rendered as follows for 0.6 version:
+
+```bash
+tar -xzf fluss-0.6.0-bin.tgz
+```
+
+## Documentation Linking
+
+### Do's
+- Use file paths with .md extensions
+``` markdown
+[Table Design](table-design/overview.md)
+```
+
+- Use paths relative to the docs/ directory
+``` markdown
+[Flink Engine](engine-flink/getting-started.md)
+```
+
+
+### Don'ts
+- Use absolute links like `/docs/` or `/blog/`
+- Use URLs without file extensions
+
+### Link Validation
+- Pull request CI checks for broken links using `.github/workflows/docs-check.yaml`
+- Fix any broken links identified in the CI build
+- Test locally with `npm run build` in the website directory
+
+## Submitting Your Contribution
+1. Commit your changes with a descriptive message:
+```bash
+git add .
+git commit -m "[docs]: add/update documentation for feature..."
+```
+2. Push to your fork:
+```bash
+git push origin feature-branch-name
+```
+3. Create a pull request on GitHub from your branch to the appropriate branch
+- For latest docs: target the main branch
+- For version-specific changes: target the specific release-x.y branch
+
+## Deployment Process
+- The `.github/workflows/docs-deploy.yaml` workflow automatically deploys documentation
+- Triggers when changes are pushed to `website/*` in any `release-*` branches or `main`
+- Runs `build_versioned_docs.sh` to collect versioned docs from all release branches