re-add core crates packages on no_std which is not imported

src/error.rs

@@ -5,6 +5,9 @@ use crate::token::Position;
 
 use crate::stdlib::{boxed::Box, char, error::Error, fmt, string::String};
 
+#[cfg(feature = "no_std")]
+use crate::alloc::string::ToString;
+
 /// Error when tokenizing the script text.
 #[derive(Debug, Eq, PartialEq, Clone, Hash)]
 pub enum LexError {