Improve trigger actions

[damianooldoni]

This small PR:

• avoids automatic checks actions will run on drafts
• allows them to be run on demand

[damianooldoni]

I noticed that actions are triggered when a set up @PietrH as reviewer. I will then remove that option. Only ready_for_review then. The syntax of [review_requested, ready_for_review] is an OR operator it seems.

[PietrH]

Shouldn't CI run on draft pull requests?

[damianooldoni]

A draft PR is still work in progress. I find annoying to have all those failures which are actually expected.

So, the idea behind this PR is:

1. you create a draft of a PR to "claim" your are working on something, so that everybody knows and in case can collaborate. You can also point to such cork in progress in case needed (answering to some issues, etc.)
2. you run automatic checks on demand on a draft whenever you want
3. once the draft is ready for review, i.e. the PR is not a draft anymore, the checks run automatically at each commit
4. you will be able to assign a reviewer afterwards once all checks pass. You can even assign a reviewer before of course, but, as you noted, it's not really "polite" 😄

Does it make sense?