Add emails checker against bugzilla workflow

A new check that checks that all new emails written in metadata.xml
correspond to existing user in bugzilla.

Signed-off-by: Arthur Zamarin <arthurzam@gentoo.org>

.github/workflows/emails.yml

@@ -6,5 +6,34 @@ jobs:
   bugzilla:
     runs-on: ubuntu-latest
     steps:
+
+    - uses: nrwl/last-successful-commit-action@v1
+      id: last_successful_commit
+      with:
+        branch: 'dev'
+        workflow_id: 'emails.yml'
+        github_token: ${{ secrets.GITHUB_TOKEN }}
+
+    - name: Checkout compare ref
+      uses: actions/checkout@v2
+      with:
+        ref: ${{ steps.last_successful_commit.outputs.commit_hash }}
+
     - name: Checkout code
       uses: actions/checkout@v2
+
+    - uses: actions/setup-python@v3
+      with:
+        python-version: '3.x'
+
+    - name: Get changed files
+      id: changed-files
+      uses: tj-actions/changed-files@v18.6
+      with:
+        base_sha: ${{ steps.last_successful_commit.outputs.commit_hash }}
+        files: |
+          **/metadata.xml
+
+    - name: Check Emails against bugzilla
+      run: |
+        python ./scripts/email-checker.py ${{ steps.changed-files.outputs.all_changed_files }}