build: need to install test-app dependencies

A prior commit removed a peerDependency on react in the top-level package.json.  This meant that react was no longer installed in the node_modules directory.  When eslint runs, that means it encountered this error:

<local path>/frontend-base/cli/test-app/src/Image.tsx
  1:38  error  Unable to resolve path to module 'react'  import/no-unresolved

The test-app (example back in frontend-build) relied on react being installed, since it’s own dependencies weren’t installed.

This commit actually runs npm ci on the test-app, as we should have been doing.  The fact that it wasn’t breaking in the past was a lucky side effect of how peer dependencies work with npm.

.github/workflows/ci.yml

@@ -21,7 +21,10 @@ jobs:
       with:
         node-version: ${{ env.NODE_VER }}
     - name: Install dependencies
-      run: npm ci
+      run: |
+        npm ci
+        cd cli/test-app
+        npm ci
     - name: Lint
       run: npm run lint
     - name: Test