Add PR title validation for Envoy 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 reviewing the reusable workflow in .github/workflows/_pull-request-lint-title.yaml and the repository's existing GitHub Actions workflows to determine the local action naming and event patterns. Add the PR title validation action and verify that it runs on PR creation, updates, reopening, and synchronization, with validation working as described.

Written by the indexing model from the issue text.