Add more detailed compile instructions

[st0nedB]

Is your feature request related to a problem? Please describe.
New users without Xcode experience might have trouble downloading and compiling the app.

Describe the solution you'd like
Step-by-Step instructions to download, compile and install the app. Possibly including external tutorials on how to install a self-developed app.

Describe alternatives you've considered
This could get obsolete, once #10 is resolved and altstore.io install is available.

Additional context

None