feat(fn): add state check functions signatures

src/lib.rs

@@ -15,6 +15,9 @@ pub trait StaticPinOps {
     fn write(data: u8);
     fn read() -> u8;
 
+    fn is_low() -> bool;
+    fn is_high() -> bool;
+
     fn set_low();
     fn set_high();
 }