Implement webhook integration with GitHub

[brazabr]

Using GitHub webhooks, implement an endpoint in GP Auto Extract to receive push notifications.

• When receive a request in the endpoint all the projects that match the pushed repo and ref (tag or branch) should then be Extract and update the originals.
• Must support both with and without secret webhook requests.

[brazabr]

@toolstack,
Should the webhook endpoint be built using the GP API router (like auto-extract is doing now) OR the WP REST API?

[toolstack]

@brazabr For something with a front end impact I'd used the GP Router, but for something that is back end only the REST API might be a better choice as we're thinking of moving to it for GP at some point in the future.

[brazabr]

Ok, REST API it is.

[Stiofan]

@brazabr have u started on this or have a timescale, i would like to have this soonish and would be happy to help out or build it. Thanks :)