github draft pr conversion to "ready for review" is ignored

[motatoes]

currently if we have a setting to ignore draft prs enabled there is an incorrect behaviour.

If a PR is currently in draft and it is marked as ready for review then digger does not react at all.

Expected behaviour is: Digger should proceed to perform a digger plan as would be the case when a PR is opened.

In the current behaviour the user has to explicitly comment "digger plan" in order to trigger the initial plan

[MrKeiKun]

@motatoes
Upon checking, It seems the issue here is that when a GitHub draft PR is converted to "ready for review", GitHub sends a ready_for_review action, but digger's code was only handling these actions:

• closed
• opened
• reopened
• synchronize
• converted_to_draft

The ready_for_review action was missing from both action filter in the backend controller and the action handling logic in the GitHub library. Gonna send this fix for this one for my hacktoberfest. Thanks