Enforcing labels on pull requests

.github/workflows/labels.yml

@@ -0,0 +1,18 @@
+name: Pull Request Labels
+"on":
+  pull_request:
+    types: [opened, reopened, labeled, unlabeled, synchronize]
+jobs:
+  label:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: mheap/github-action-required-labels@v1
+        with:
+          mode: minimum
+          count: 1
+          labels: "s-feature, m-feature, l-feature, build, refactor, tests, documentation, bug, enhancement"
+      - uses: mheap/github-action-required-labels@v1
+        with:
+          mode: exactly
+          count: 0
+          labels: "do not merge"