Upgrade CLA check scripts from aicore/contributor-license-agreement

[abose]

• [x] New features added to CLA check infra from https://github.com/aicore/contributor-license-agreement should be imported into this repo for brackets
• [x] Validate features are working as expected (comment bots, cla sign check use cases)

[psdhanesh7]

• [x] New features added to CLA check infra from https://github.com/aicore/contributor-license-agreement should be imported into this repo for brackets
• [x] Validate features are working as expected (comment bots, cla sign check use cases)
• Task 1: Completed with pull requests https://github.com/brackets-cont/contributor-license-agreement/pull/21#issue-1221721400 and https://github.com/brackets-cont/contributor-license-agreement/pull/24#issue-1221781271
• Task 2: Verified changes are working as expected in pull request https://github.com/brackets-cont/contributor-license-agreement/pull/25#issue-1221785071

[abose]

Thanks for fixing the issue @psdhanesh7