Use GH action to publish coverage badge.

.github/workflows/test_fast.yml

@@ -36,6 +36,34 @@ jobs:
     - name: Run fast tests
       run: |
         hatch -v run test -m "not slow"
+        - name: Run coverage
+        run: |
+          coverage run ...
+          coverage report -m
+
+    - name: Coverage Badge
+      uses: tj-actions/coverage-badge-py@v2
+
+    - name: Verify Changed files
+      uses: tj-actions/verify-changed-files@v16
+      id: verify-changed-files
+      with:
+        files: coverage.svg
+
+    - name: Commit files
+      if: steps.verify-changed-files.outputs.files_changed == 'true'
+      run: |
+        git config --local user.email "github-actions[bot]@users.noreply.github.com"
+        git config --local user.name "github-actions[bot]"
+        git add coverage.svg
+        git commit -m "Updated coverage.svg"
+
+    - name: Push changes
+      if: steps.verify-changed-files.outputs.files_changed == 'true'
+      uses: ad-m/github-push-action@master
+      with:
+        github_token: ${{ secrets.github_token }}
+        branch: ${{ github.ref }}
 
   publish:
     name: Publish to PyPI