Extract reading of input i/o to input

And add the ability of other modules to listen to either
the final result (a `Key`) or tap into the input as it is read

test/mpv/control_test.gleam

@@ -3,7 +3,7 @@ import gleeunit
 
 import input/key.{type Key, Char}
 import mpv/control.{type Control}
-import mpv/internal/control as control_internal
+import mpv/internal as control_internal
 
 pub fn main() -> Nil {
   gleeunit.main()