Extract T5 module and add main function to use it (#829)

* Extract t5 out of musicgen

* Add main for t5 module

candle-examples/examples/musicgen/main.rs

@@ -13,7 +13,6 @@ extern crate accelerate_src;
 mod encodec_model;
 mod musicgen_model;
 mod nn;
-mod t5_model;
 
 use musicgen_model::{GenConfig, MusicgenForConditionalGeneration};