Add linting check for commit messages

[gdemonet]

Component: git

Why this is needed:

We have decided of a format for our Git commit messages (see our best practices), but it is not enforced yet.

What should be done:

We want to enforce this format through a linting check.

Implementation proposal (strongly recommended):

• Add some GitHub Action to enforce this check on all PRs (something like:

# .github/workflows/commitlint.yml
---
name: "Lint Commit Messages"
"on":
  - "pull_request"jobs:
  commitlint:
    runs-on: "ubuntu-latest"
    steps:
      - uses: "actions/checkout@v2"
        with:
          fetch-depth: 0
      - uses: "wagoid/commitlint-github-action@v2.1.0"

credits to @NicolasT)

• Add the exact same linter to Eve steps (as part of our lint stage), to make sure an Eve pre-merge run is self-sufficient

Test plan:

Invalid commit messages should never land in this repository anymore.

[NicolasT]

You'll likely also need to write a Commitlint config to match what we want to enforce/allow. For Eve, use commitlint in CLI mode (can also be used as a post-commit hook in dev environments of course). Or add it to the lint buildchain target?