Day 5 — PR Automation: Auto-Labels, Size Checks, and Statistics

Reviewing pull requests is easier when you can see at a glance what changed and how large the PR is.

Day 5 automates three things

labelling PRs based on which files changed,

adding a size label, and

posting a statistics comment.

WorkFlow

Three separate jobs running in parallel on every PR.

Job 1 — Auto-label by file type

```yaml
- name: Label based on files changed
  uses: actions/github-script@v7
  with:
    script: |
      const { data: files } = await github.rest.pulls.listFiles({...});
      const labels = new Set();
      
      for (const file of files) {
        const path = file.filename;
        if (path.includes('.github/workflows/')) labels.add('workflows');
        if (path.startsWith('src/'))             labels.add('source-code');
        if (path.includes('.test.'))             labels.add('tests');
        if (path.endsWith('.md'))                labels.add('documentation');
        if (path === 'package.json')             labels.add('dependencies');
        if (path.endsWith('.css'))               labels.add('styles');
        if (path.includes('components/'))        labels.add('components');
      }
      
      if…