refactor: Remove std but add alloc

src/lib.rs

@@ -1,3 +1,9 @@
+#![no_std]
+extern crate alloc;
+use crate::alloc::borrow::ToOwned;
+use alloc::format;
+use alloc::string::{String, ToString};
+
 pub mod display;
 
 #[derive(Copy, Clone)]