Missing contributing guidelines

[vil02]

Describe the bug in a sentence or two.

The target of the link:

cloudinary_java/README.md

Line 130 in 43d8e9a

See [contributing guidelines](/CONTRIBUTING.md).

does not exist.

Issue Type (Can be multiple)

[ ] Build - Can’t install or import the SDK
[ ] Performance - Performance issues
[ ] Behaviour - Functions aren’t working as expected (Such as generate URL)
[ ] Documentation - Inconsistency between the docs and behaviour
[x] Other (Specify)

[debnath003]

I would like to work on this. Can you assign it to me?

[michal-sordyl-cloudinary]

@debnath003 Thanks for PR, we will review it!