Introduced heartbeat endpoint and changed main url route to /api

Just a little change in the main api endpoint to /api and renamed ping endpoint to heartbeat.

\approve @prehn

obmdataapi/__init__.py

@@ -31,14 +31,11 @@ logger.info("obmapidata has started")
 app = Quart(__name__)
 app.api = JSONRPCQuart()
 
-app.route(
-    "/",
-    methods=[
-        "POST",
-    ],
+app.post(
+    "/v1",
 )(app.api.handler)
 
 
 @app.api.add_function
-async def ping():
-    return "pong"
+async def heartbeat() -> dict:
+    return {"status": "healthy"}