Update docs workflows

.github/workflows/doc-cleanup.yaml

@@ -0,0 +1,26 @@
+name: Doc Preview Cleanup
+
+on:
+  pull_request:
+    types: [closed]
+
+jobs:
+  doc-preview-cleanup:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout gh-pages branch
+        uses: actions/checkout@v2
+        with:
+          ref: gh-pages
+      - name: Delete preview and history + push changes
+        run: |
+            if [ -d "previews/PR$PRNUM" ]; then
+              git config user.name "richardreeve"
+              git config user.email "git@richardreeve.net"
+              git rm -rf "previews/PR$PRNUM"
+              git commit -m "delete preview"
+              git branch gh-pages-new $(echo "delete history" | git commit-tree HEAD^{tree})
+              git push --force origin gh-pages-new:gh-pages
+            fi
+        env:
+            PRNUM: ${{ github.event.number }}

.github/workflows/docs.yaml

@@ -6,10 +6,13 @@ on:
       - dev
     tags:
       - 'v*'
+  pull_request:
   workflow_dispatch:
 
 jobs:
   build:
+    permissions:
+      contents: write
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code