Moved frontend/index.html to frontend/html/index.html

Closing #2; Closing #1

backend/rest_api.py

@@ -22,7 +22,7 @@ def handle_first_launched():
 
 @app.get("/")
 @app.get("/<path:url_path>")
-def handle_get(url_path: str = "index.html") -> Response:
+def handle_get(url_path: str = "html/index.html") -> Response:
     """
     Handle all get requests that are made.
     """