feat: diff of states

Added first subcommand - diff.
It allows to check how diffrent
current state of machine is in
compareson to world file.

src/error.rs

@@ -0,0 +1,3 @@
+pub type Error = std::boxed::Box<dyn core::error::Error>;
+
+pub type Result<T> = core::result::Result<T, Error>;