Create makefile to make MacOS .app bundle

[JoseVarelaP]

Given right now the applications builds as a unix executable, I wanted to make it compile and show itself as a proper .app bundle, this PR aims to do such thing.

Stuff to do:

• Create icns and base .app bundle to generate the unix executable.
• Create makefile that deals with copying the unix to the .app bundle.
• Make instance to perform the same action on a debug build
• Look into making the makefile not Mac-exclusive (if possible).

In action:

[JoseVarelaP]

Nevermind this, I just noticed the build-actions already generates this via cargo-bundle.