fix: improve how we detect that the PR is managed by Mergify (#37)

The previous fix doesn't work on the old GitHub UI because the check-runs aren't built the same way. This PR adds a new way to find Mergify's icon on the page.

Fixes MRGFY-4595

fix: improve how we detect that the PR is managed by Mergify (#36)

The former implementation can detect any Mergify App icon in the page, even if the PR has been referenced by another one. We have to look for the "Summary" or the "Merge Protections" check-run.

Fixes MRGFY-4553

fix: improve how we find the new merge box (#35)

The conflict section isn't always there (when the pull request is up to date). As the merge box hasn't a distinct class or id, we have to look for others sections like Checks or Reviews.

fix: inject buttons in the right place (#34)

The new merge box selector is too generic. We have to select a section with a precise selector. The conflict section is always injected so we can select it and get the parent element to inject Mergify's buttons.

Fixes MRGFY-4504
Fixes #33

fix: inject buttons only on pull request page (#31)

Fixes MRGFY-4496

feat: support new GitHub merge box (#30)

Fixes MRGFY-4360

revert: "feat: support new GitHub merge box" (#28)

Reverts #27

GitHub is slowed down once the extension is updated. We have to rework this change.

feat: support new GitHub merge box (#27)

chore: update logos (#25)

Change-Id: Ide80de2fad2039ca73242ee5794ba373f76220a5

fix: use new link format (#23)