Trigger CI when PRs are created/updated

[peterstace]

Description

Right now, CI is not run when PRs are raised against forks. By adding pull_request as a triggering action, I think this will cause them to run for forks as well (this is a little bit experimental).

References:

• https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#push

• https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request

Check List

Have you:

• Added unit tests? N/A

• Add cmprefimpl tests? (if appropriate?) N/A

• Updated release notes? (if appropriate?) N/A

Related Issue

N/A

Benchmark Results

N/A

[peterstace]

Hmm, this seems to be running the action twice, which is not what I intended...