doc: create contribution document

CONTRIBUTING.md

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+
+## How to contribute to Sonic
+
+#### **Did you find a bug?**
+
+
+* **Do not open up a GitHub issue if the bug is a security vulnerability
+  in Sonic**, and instead to refer to our security policy.
+
+* **Ensure the bug was not already reported** by searching on GitHub under [Issues](https://github.com/go-sonic/sonic/issues).
+
+* If you're unable to find an open issue addressing the problem, [open a new one](https://github.com/go-sonic/sonic/issues/new). Be sure to include a **title and clear description**, as much relevant information as possible, and a **code sample** or an **executable test case** demonstrating the expected behavior that is not occurring.
+
+
+#### **Did you write a patch that fixes a bug?**
+
+* Open a new GitHub pull request with the patch.
+
+* Ensure the PR description clearly describes the problem and solution. Include the relevant issue number if applicable.
+
+#### **Did you fix whitespace, format code, or make a purely cosmetic patch?**
+
+Changes that are cosmetic in nature and do not add anything substantial to the stability, functionality, or testability of Sonic will generally not be accepted .
+
+#### **Do you intend to add a new feature or change an existing one?**
+
+* Suggest your change in the [Issue](https://github.com/go-sonic/sonic) and start writing code.
+
+#### **Do you have questions about the source code?**
+
+* Ask any question about how to use Sonic in the [Discussions](https://github.com/go-sonic/sonic/discussions).
+
+
+
+
+Thanks! :heart: :heart: :heart:
+
+Go-Sonic