Add placeholder workflow for updating dependencies. (#628)

* Add placeholder workflow for updating dependencies.

Author: jonsimantov

.github/workflows/update-dependencies.yml

@@ -0,0 +1,13 @@
+name: Update Android and iOS dependencies (placeholder)
+on:
+  workflow_dispatch:
+    inputs:
+
+jobs:
+  update_dependencies:
+    name: update-dependencies
+    runs-on: ubuntu-latest
+    steps:
+      - name: Placeholder step
+        run: |
+          true