[docs] edits contributing guide
[docs] edits contributing guide

nimblecode/nimblecode,marksanghoonkim/nimblecode,nimblecode/nimblecode,rickyeh/nimblecode,nimblecode/nimblecode,rickyeh/nimblecode,LinearAtWorst/cogile,marksanghoonkim/nimblecode,marksanghoonkim/nimblecode,LinearAtWorst/cogile,rickyeh/nimblecode,marksanghoonkim/nimblecode,nimblecode/nimblecode,rickyeh/nimblecode