[Build] Move manifest to .well-known/

The location of IWA manifest was changed from `/manifest.webmanifest` to
`/.well-known/manifest.webmanifest` [1]. Reflect that change in our
sample IWA.

[1] More discussion: WICG/isolated-web-apps#24

diagnostics-app/build_iwa.sh

@@ -16,7 +16,7 @@ web_bundle=$(mktemp)
 
 # Copy the files into the temporary folders
 cp -r dist/diagnostics-app/* ${iwa_src}
-cp -r iwa/public/* ${iwa_src}
+cp -r iwa/public/. ${iwa_src}
 
 # Create the bundle
 wbn --dir ${iwa_src} --output ${web_bundle} --formatVersion b2

diagnostics-app/iwa/public/.well-known/manifest.webmanifest

@@ -0,0 +1,21 @@
+{
+  "name": "Diagnostics App IWA",
+  "id": "/",
+  "scope": "/",
+  "start_url": "/",
+  "version": "0.1.0",
+  "display": "standalone",
+  "icons": [
+    {
+      "src": "/icon.png",
+      "type": "image/png",
+      "sizes": "512x512",
+      "purpose": "any maskable"
+    }
+  ],
+  "permissions_policy": {
+    "camera": ["self"],
+    "microphone": ["self"],
+    "fullscreen": ["self"]
+  }
+}