CI: Check that JSDoc comments are valid (#1328)

Also, fix a JSDoc comment.

.github/workflows/docs.yml

@@ -0,0 +1,19 @@
+name: Documentation
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  lint:
+    name: JSDoc
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-node@v1
+    - run: npm ci
+    - run: npm run docs