ENH - Add RTD preview action (#27)

Author: trallard

.github/workflows/rtd-preview.yml

@@ -0,0 +1,18 @@
+# Add a link to the documentation preview in the PR description.
+
+name: rtd preview link
+on:
+  pull_request_target:
+    types:
+      - opened
+
+permissions:
+  pull-requests: write
+
+jobs:
+  documentation-links:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: readthedocs/actions/preview@v1
+        with:
+          project-slug: "bokeh-a11y-audit"