Added a comment for PID struct

src/core/logic/pid.rs

@@ -17,6 +17,8 @@ pub struct Config {
     pub accel: f32,
 }
 
+///A PID, the config field is used to handle all the needed configuration.
+/// This PID using pid_step() then attempts to output a value between -1.0 and 1.0 to attempt to make the "current_value" passed in, match the "set_point"
 pub struct PID {
     pub config: Config,