Add Instructions on Running Tests to the Contributions Guide (radius-…

…project#6926)

# Description

Update the contributions guide to include link to the instructions on
running Radius tests.

## Type of change

<!--

Please select **one** of the following options that describes your
change and delete the others. Clearly identifying the type of change you
are making will help us review your PR faster, and is used in authoring
release notes.

If you are making a bug fix or functionality change to Radius and do not
have an associated issue link please create one now.

-->

- This pull request is a minor refactor, code cleanup, test improvement,
or other maintenance task and doesn't change the functionality of Radius
(issue link optional).

## Auto-generated summary

<!--
GitHub Copilot for docs will auto-generate a summary of the PR
-->

<!--
copilot:all
-->
### <samp>🤖[[deprecated]](https://githubnext.com/copilot-for-prs-sunset)
Generated by Copilot at 9055e8f</samp>

### Summary
:link::test_tube::memo:

<!--
1. :link: This emoji represents the addition of a link to the table of
contents. It conveys the idea of connecting or referencing another part
of the document.
2. :test_tube: This emoji represents the topic of running tests for the
radius project. It conveys the idea of experimentation, verification, or
quality assurance.
3. :memo: This emoji represents the update of the documentation in the
`CONTRIBUTING.md` file. It conveys the idea of writing, editing, or
informing.
-->
Added a link to the `Run tests` section in `CONTRIBUTING.md`. This
improves the accessibility of the testing documentation for
contributors.

> _`Run tests` section_
> _Added to the contents list_
> _Helps contributors_

### Walkthrough
* Add link to `Run tests` section in table of contents
([link](https://github.com/radius-project/radius/pull/6926/files?diff=unified&w=0#diff-eca12c0a30e25b4b46522ebf89465a03ba72a03f540796c979137931d8f92055R14))

Signed-off-by: karishma-chawla <[email protected]>
Co-authored-by: karishma-chawla <[email protected]>

CONTRIBUTING.md

@@ -11,6 +11,7 @@ You can find our full **contributor documentation** including instructions at th
 - [Install prerequisites](./docs/contributing/contributing-code/contributing-code-prerequisites/)
 - [Create your first commit (full walkthrough)](./docs/contributing/contributing-code/contributing-code-first-commit/)
 - [Building the repo](./docs/contributing/contributing-code/contributing-code-building/)
+- [Run tests](./docs/contributing/contributing-code/contributing-code-tests/README.md)
 - [Understanding repo organization](./docs/contributing/contributing-code/contributing-code-organization/)
 - [Contribute to issues](./docs/contributing/contributing-issues/)
 - [Create pull requests](./docs/contributing/contributing-pull-requests/)