ci: check that docs don't need to be regenerated

.github/workflows/lint.yml

@@ -13,6 +13,24 @@ jobs:
           configFile: './package.json'
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+  docs:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - uses: actions/setup-node@v2.1.0
+        with:
+          node-version: 12.x
+      - name: install
+        run: yarn
+      - name: regenerate docs
+        run: yarn tools:regenerate-docs
+      - name: report regenerated docs
+        run: |
+          git diff --name-only \
+            | xargs -I '{}' bash -c \
+              'echo "::error file={}::This needs to be regenerated by running \`tools:regenerate-docs\`" && false'
   danger:
     runs-on: ubuntu-latest
     steps: