Add review comment action

.github/workflows/review.yml

@@ -0,0 +1,25 @@
+---
+name: Add review url
+
+on:
+  pull_request_target:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: peter-evans/find-comment@v2
+        id: fc
+        with:
+          issue-number: ${{ github.event.pull_request.number }}
+          comment-author: 'github-actions[bot]'
+          body-includes: Automated Review URLs
+
+      - uses: peter-evans/create-or-update-comment@v2
+        with:
+          comment-id: ${{ steps.fc.outputs.comment-id }}
+          issue-number: ${{ github.event.pull_request.number }}
+          body: |
+            #### Automated Review URLs
+            * [render latest/index.bs](http://api.csswg.org/bikeshed/?url=https://raw.githubusercontent.com/GraphBLAS/binsparse-specification/${{ github.event.pull_request.head.sha }}/latest/index.bs)
+          edit-mode: replace