Adding contribution.md for contribution guidelines

[jesutobi]

@alswajiab @BatoolMM there was conflict on that branch , which was preventing its merge, trying to resolve it now by creating a new pull request.
fixes #125
This is a contribution .md file that helps new contributors find it easy to contribute to OSCSA website

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[jesutobi]

@BatoolMM good evening , my pull request hasn't been reviewed since i made corrections to it, i dont know what to do next

[BatoolMM]

I love the way you have written the contribution guidelines - there is minor corrections if you can go through them. Thank you so much!

[jesutobi]

I love the way you have written the contribution guidelines - there is minor corrections if you can go through them. Thank you so much!

Thank you for your time, i have also resolved all the suggested changes

[jesutobi]

@BatoolMM i have made changes to the ones you suggested, thank you