Add PR title validation for ML Metadata operator repository using reusable workflow

### Context

Ensuring PR titles (and merge commits) always follow a defined naming convention is necessary to maintain a clean and readable repository.

Ref: https://github.com/canonical/bundle-kubeflow/issues/1376

### What needs to get done

1. Add new action, possibly named on_pull_request_lint_title, which uses the reusable workflow defined [here](https://github.com/canonical/charmed-kubeflow-workflows/blob/main/.github/workflows/_pull-request-lint-title.yaml)

### Definition of Done

1. Action runs when a PR is created, updated, reopened or synchronized
2. PR title validation is working

Start by reading the reusable workflow at .github/workflows/_pull-request-lint-title.yaml in charmed-kubeflow-workflows and inspect the mlmd-operator repository's existing GitHub Actions. Add the new pull-request title lint action with the requested triggers, then verify that PR title validation runs when a pull request is created, updated, reopened, or synchronized.

Written by the indexing model from the issue text.