feat(ci): label docs-related PRs

Author: thekaveman

.github/workflows/labeler-docs.yml

@@ -0,0 +1,19 @@
+name: Label docs
+
+on:
+  pull_request:
+    branches: [main]
+    types: [opened]
+    paths:
+      - "docs/**"
+      - "mkdocs.yml"
+      - ".github/workflows/mkdocs.yml"
+
+jobs:
+  label-docs:
+    runs-on: ubuntu-latest
+    steps:
+      - name: add-label
+        uses: andymckay/labeler@master
+        with:
+          add-labels: "documentation"