feat(ci): pr-validate.yml for pr descriptions

[DerekRoberts]

• [x] separate non-critical workflow (pr description, conventional commits?)

Pulled out from https://github.com/bcgov/nr-fom/pull/576

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Thanks for the PR!

Any successful deployments (not always required) will be available below.

• api
• admin
• public

Once merged, code will be promoted and handed off to following workflow run.

• Main Merge Workflow