Grey icon for PWA

Summary:
Right now, both Launcher and PWA share the same icon.

As to make it easier to identify which one is which, PWA will have a greyed icon instead.

Reviewed By: antonk52

Differential Revision: D47436998

fbshipit-source-id: 69d4d273c35e327263fbbf02d4ac7a005013f1d9

desktop/scripts/build-flipper-server-release.tsx

@@ -228,6 +228,7 @@ async function copyStaticResources(outDir: string, versionNumber: string) {
     'icon.icns',
     'icon.ico',
     'icon.png',
+    'icon_grey.png',
     'icons.json',
     'index.web.dev.html',
     'index.web.html',