docs: improve the contribution guide [ci skip]

Author: hakimio

CONTRIBUTING.md

@@ -1,31 +1,77 @@
 # Contributing Guide
 
-Thank you for your interest in contributing to our project! We welcome all contributions, from bug reports to new features.
+Thank you for your interest in contributing to our project! We welcome all contributions, from **bug reports** to **new
+features**.
 
-This guide will help you get started quickly.
+This guide will help you **get started quickly**.
 
 ## How to Contribute
 
 There are several ways to contribute, even if you don't want to write code.
 
 1.  **Report a Bug:** Open an issue to tell us about something that's broken.
 2.  **Suggest a Feature:** Open an issue to propose a new idea.
-3.  **Fix a Bug or Implement a Feature:** Submit a Pull Request (PR) with your code changes.
+3.  **Fix a Bug or Implement a Feature:** Submit a **Pull Request (PR)** with your code changes.
+
+---
 
 ## Quick Start for Code Contributions
 
 If you're ready to submit code, follow these steps:
 
 ### 1. Find an Issue
-Look through the [open issues](../../issues) to find something you'd like to work on. If you're new, look for labels like `good first issue` or `help wanted`. If you want to work on something new, **please open an issue to discuss it first** before writing code.
+
+Look through the [open issues](../../issues) to find something you'd like to work on. If you're new, look for labels
+like `good first issue` or `help wanted`. If you want to work on something new, **please open an issue to discuss it
+first** before writing code.
 
 ### 2. Fork the Repository
-Click the "Fork" button in the top right of this repository's page. This creates your own copy of the project under your GitHub account.
+
+Click the **"Fork"** button in the top right of this repository's page. This creates your own copy of the project under
+your GitHub account.
 
 ### 3. Clone Your Fork
+
 Clone your forked repository to your local machine.
 
 ```bash
 git clone https://github.com/angular-ru/sdk.git
-cd repository-name
+cd sdk
+# Switch to the main branch.
+git checkout main
+# Create a new branch for your changes.
+git checkout -b my-bug-fix
 ```
+
+You can find more information about Git feature branches
+[here](https://www.atlassian.com/git/tutorials/comparing-workflows/feature-branch-workflow).
+
+### 4. Start the Project
+
+1. Run `npm ci` to install dependencies.
+2. Run `nx serve` to serve one of the demo apps. For example:
+
+```bash
+nx serve virtual-table-demo
+```
+
+---
+
+## Testing
+
+Make sure your changes pass existing tests and that you write **new tests** for any new or changed behavior:
+
+- `npm run test` to run unit tests
+- `npm run lint` to run the linter
+- `npm run build:lib:all` to build all libraries
+- `npm run build:app:all` to build all demo apps
+
+---
+
+## Pull Request Process
+
+1. We follow [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) for our commit messages. For
+   example: `feat(cdk): improve typing`
+2. Ensure you **cover all code changes with unit tests**.
+3. When you are ready, create a **Pull Request** in GitHub targeting the `main` branch.
+4. We will review your code and merge it if everything is okay!