Solved : Add Contribution.md #6

[Santhosh-Siddhardha]

Made changes in Contribution.md

• Added Documentation Section
• Added Code reviews section
• Added Feature Requests section
• Added Spread the word section

[Santhosh-Siddhardha]

@TusharAMD Could you please add gssoc label.

[Santhosh-Siddhardha]

@TusharAMD Please add gssoc and level label, otherwise points will not be counted, Please assign labels to PR