Add GH action for static analysis tool mobsfscan

This action is configured to run nightly or manually.
That might change after we've went through and fixed
or suppressed some of reported issues.

.github/workflows/android-static-analysis.yml

@@ -0,0 +1,23 @@
+---
+name: Android - Static analysis
+on:
+  schedule:
+    # At 06:20 UTC every day.
+    # Notifications for scheduled workflows are sent to the user who last modified the cron
+    # syntax in the workflow file. If you update this you must have notifications for
+    # Github Actions enabled, so these don't go unnoticed.
+    # https://docs.github.com/en/actions/monitoring-and-troubleshooting-workflows/notifications-for-workflow-runs
+    - cron: '20 6 * * *'
+  workflow_dispatch:
+jobs:
+  mobsfscan:
+    name: Code scanning using mobsfscan
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Scan code
+        uses: MobSF/mobsfscan@main
+        with:
+          args: '--type android android'