Refresh dependencies

It's not like we need any new features, but let's bump the versions
because we are in JavaScript land.

Also, run "npm audit" regularly, just in case a serious vulnerability
is discovered.

.github/workflows/main.yml

@@ -27,3 +27,11 @@ jobs:
         run: |
           cl.exe hello.c
           hello.exe
+  audit:
+    name: npm audit
+    runs-on: windows-latest
+    steps:
+      - name: Check out source code
+        uses: actions/checkout@v1
+      - run: npm install
+      - run: npm audit