Add PR auto-approve option

[R0Wi]

Problem:
Personally i use Github branch protection rules to prevent merging into stable and master-branches without a pull request review. This prevents the fork-sync action to automatically merge the changes of the forked repository into my personal fork. Generally speaking i don't want to change the branch-protection-rules because when talking about regular code-changes these make perfectly sense to me.

What this change implements:
This PR adds a new feature "auto-approve" which can be activated optionally by setting auto_approve and personal_token input variables. After the pull request is created by the fork-sync action the auto_approve variable will be checked. If it's set to true the action will approve the changes made by the pull request created before with the user which belongs to the personal_token. Also a comment on this review will be generated which makes it clear that this review was automatically generated. Afterwards the github-actions bot is able to merge the pull request.

A possible result will look like this:

This changes solves:
Branch protection rules regarding the review process can exist next to the fok-sync action.

Also in this PR:
When testing i noticed that there was a situation where an error occured and error.errors was set and contained one element which had no message property so i received Cannot read property 'startsWith' of undefined.

fork-sync/src/main.ts

Line 35 in 9671705

if (!!error.errors && error.errors[0].message.startsWith('No commits between')) {

I improved this, too.

Let me know what you think about this

Cheers :-)

[tgymnich]

shouldn't the already used GITHUB_TOKEN have sufficient permissions to review and approve PRs?

[R0Wi]

Tested it but Github gave me an error message like "you cannot approve your own pull request" which makes sense somehow ;-)

So there have to be two different users then

[tgymnich]

Thank you for your contribution!