Add license to idle loops

[bary12]

Currently, idle loops doesn't have a license file. This means that

without a license, the default copyright laws apply, meaning that you retain all rights to your source code and no one may reproduce, distribute, or create derivative works from your work.

(from Github docs)

Idle Loops has already been forked and development continued on other forks (omsi6 -> lloyd-delacroix -> mopatissier), and even stopsign.github.io links to the omsi6 version. The fact that Idle Loops doesn't have a license may cause problems for the continual development of the game

@StopSign