Hooks integration to fetch issues and PRs.

[RonLek]

As a GitHub app developer
I Need to: create webhooks for GitHub API
So That: I can fetch issues and PRs directly within Rocket.Chat

Acceptance Criteria

• Document the approach taken with diagrams for user flow.

[RonLek]

@samad-yar-khan could you please provide documentation over the approach you're planning to take so I can refine the acceptance criteria better?

[samad-yar-khan]

@RonLek I have added the workflow and how the works along with some code explanations in the Wiki.

[RonLek]

Thanks @samad-yar-khan . Could you please confirm if #7 already added this one so I can mark this as complete?

[samad-yar-khan]

@RonLek It was not part of the pull request but I have added the documentation to project wiki :
[https://github.com/RocketChat/Apps.Github22/wiki/GitHub-Event-Subscriptions](GitHub event subscription user flow). Let me know if anything else is required.

[RonLek]

LGTM