Move docs pipelines to use Actions (#24434)

similar to #24314, this moves drone cron pipelines to (GitHub) Actions.
As these are mostly compatible with Gitea Actions, when we start to
dogfood, these will already be migrated.

I also removed the discord notify pipeline, as it hasn't been working
for several months.

.github/workflows/pull-compliance_docs.yml

@@ -0,0 +1,22 @@
+name: Compliance testing for documentation
+
+on:
+  pull_request:
+    paths:
+      - "docs/**"
+      - "*.md"
+
+jobs:
+  compliance-docs:
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout
+        uses: actions/checkout@v3
+      - name: setup node
+        uses: actions/setup-node@v2
+        with:
+          node-version: 18
+      - name: install dependencies
+        run: make deps-frontend
+      - name: lint markdown
+        run: make lint-md