The current triggers require a push or PR to exercise the pipeline. Adding this trigger will allow the pipeline to be run without having to modify any code.

for Black Code Formatter build step

For Mypy check build step

They are check actions not critical for the build so makes sense to have them in a different job running on Linux (since the actions require linux) and then have the build job depend on the check job.

Fixes the following in workflow runs:
```
Node.js 12 actions are deprecated. For more information see: https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/. Please update the following actions to use Node.js 16: actions/checkout, actions/checkout
```

v3 -> v4