adding a new core module

This module will hold all the core mechanincs so that we can abstract
things further and allow for a better design of the main system. This
gives the freedom of moving the ui further from the logic and allows
for changing the ui in the future.

src/rust/lib.rs

@@ -13,4 +13,5 @@ pub mod utils;
 pub mod video_model;
 pub mod ytdl;
 pub mod slide_types;
+pub mod core;
 // mod video_thumbnail;