Add AppLoading component

[dincozdemir]

Problem:
As of now, the application does not have a loading state. When something is being fetched, the screen just waits at its state. This creates a bad user experience and we need to show that the app is running/fetching something in the background.
Requirement:
We need an isolated loading screen that could be re-used. So that we can show the users that the app is not dead, but is just running/fetching something in the background.