Add contribution guide

[saini-g]

Add a CONTRIBUTING.md file to help anyone willing to contribute.
It should contain some basic information:

• How to setup and test the component locally
• Contribution doesn't mean you have to write code, what other different types of contributions someone can make. eg: Raising and issue, requesting a feature, fixing a typo in the docs, and many more...
• Tips on writing good & consistent code, writing better docs, raising issues the right way, etc.

It will be a constantly evolving document, so it doesn't need to be perfect on the first try, but try to get as much as you can in there.

Thanks a ton in advance! 😃