Add missing PWA icon (#1060)

- Copy old icon back into repository
- Update path to icon from manifest file
- Add link metadata tag for iOS PWA icon to workbench.html
- Add link metadata tag for iOS PWA icon to login page

src/media/manifest.json

@@ -6,8 +6,8 @@
 	"background-color": "#fff",
 	"description": "Run VS Code on a remote server.",
 	"icons": [{
-		"src": "static/code-server.png",
-		"sizes": "128x128",
+		"src": "./static/out/vs/server/src/media/code-server.png",
+		"sizes": "384x384",
 		"type": "image/png"
 	}]
 }