Update Contributing guidelines document

[senthilrch]

https://github.com/senthilrch/kube-fledged/blob/master/CONTRIBUTING.md needs to be updated as follows:-

We invite contributions to kube-fledged.

• Submit an issue if you find a bug or interested in seeing a new feature/ enhancement implemented.
• If you would like to submit a PR for an existing issue, please make a comment in the issue. The maintainer will review your request and if approved, the issue will be assigned to you.
• Once the issue is assigned to you, start working on the issue.
• Fork the project, develop and test your code.
• Submit a pull request against 'develop' branch. Ensure ALL CI checks are passed.
• The maintainer will review and approve your pull request

[shelar1423]

Hey, kindly assign this to me

[senthilrch]

Done