chore: Add typedoc.

.github/workflows/ci.yml

@@ -72,3 +72,13 @@ jobs:
         with:
           github-token: ${{ secrets.github_token }}
           parallel-finished: true
+
+  docs:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v1
+        with:
+          node-version: 14.x
+      - run: npm ci --ignore-scripts
+      - run: npm run docs