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

src/key/helper.js

@@ -217,7 +217,7 @@ export async function createSignaturePacket(dataToSign, privateKey, signingKeyPa
  * @param {Object} dest
  * @param {String} attr
  * @param {Date} [date] - date to use for signature expiration check, instead of the current time
- * @param {(SignaturePacket) => Boolean} [checkFn] - signature only merged if true
+ * @param {Function} [checkFn] - signature only merged if true
  */
 export async function mergeSignatures(source, dest, attr, date = new Date(), checkFn) {
   source = source[attr];