Add support for post-push hook

[robko23]

As the title says. A hook that would run right after it finished pushing commit.

This could be used to trigger automated builds only for the projects that have changed

[chaaz]

Hey, @robko23, been thinking about this one a lot. I've created PR #27 to do similar to your proposal, but fitting a bit better within the current behavior. I'm also considering adding more info functionality (simply listing projects that will be / have had their version changed) so that you can trigger automated builds yourself in whatever CI/CD system you want. Let me know what you think.

[brandonguigo]

Hey, @robko23, been thinking about this one a lot. I've created PR #27 to do similar to your proposal, but fitting a bit better within the current behavior. I'm also considering adding more info functionality (simply listing projects that will be / have had their version changed) so that you can trigger automated builds yourself in whatever CI/CD system you want. Let me know what you think.

Hey @chaaz, I think listing projects that will have thir version bumped with the next planned version could be very useful for pre-releases #28