Improve responsiveness of UI startup by not waiting for render threads to start up before showing the UI. Errors while starting the render thread will be logged anyway, so there's no need to block the main thread for this

ui/main.py

@@ -1,5 +1,5 @@
 from easydiffusion import model_manager, app, server
-from easydiffusion.server import server_api # required for uvicorn
+from easydiffusion.server import server_api  # required for uvicorn
 
 # Init the app
 model_manager.init()
@@ -8,3 +8,5 @@ server.init()
 
 # start the browser ui
 app.open_browser()
+
+app.init_render_threads()