Show more granular status of PR checks

[nathonius]

Current implementation only looks at a true/false mergeability, so regardless of the reason a PR isn't mergeable (conflicts, reviews, checks), it will just show 'not mergeable'.

Calling the checks endpoint would allow for much more granular data, but requires a bit more effort than I'm interested in investing right now. Same with review comments.

[claremacrae]

Thanks for this really useful plugin...

Would this request cover searches like:

is:pr is:open -is:draft status:success?

• -is:draft to only show non-Draft PRs
• status:success to show ones that passed CI?

Asking to avoid creating duplicate requests for those if one exists already...

[claremacrae]

This works:

```github-query
outputType: table
queryType: pull-request
query: "repo:obsidian-tasks-group/obsidian-tasks state:open is:pr is:open -is:draft status:success"
```