fix: add syntax highlighting in comments and README

README.md

@@ -283,7 +283,7 @@ match cmd.parse_until_sub_cmd() {
 
 This crate supports Rust 1.74.1 or later.
 
-```
+```sh
 % cargo msrv --no-check-feedback
 Fetching index
 Determining the Minimum Supported Rust Version (MSRV) for toolchain x86_64-apple-darwin

src/lib.rs

@@ -149,7 +149,7 @@
 //!
 //! In addition,the help printing for an array of [OptCfg] is generated with [Help].
 //!
-//! ```
+//! ```rust
 //! use cliargs::{Cmd, OptCfg};
 //! use cliargs::OptCfgParam::{names, has_arg, defaults, validator, desc, arg_in_help};
 //! use cliargs::validators::validate_number;
@@ -238,7 +238,7 @@
 //! If you want to specify an array which contains only one emtpy string, write nothing after `=` symbol, like
 //! `#[opt(cfg="=")]`.
 //!
-//! ```
+//! ```rust
 //! use cliargs::Cmd;
 //! use cliargs::errors::InvalidOption;
 //! use cliargs::Help;
@@ -289,7 +289,7 @@
 //!
 //! The folowing is an example code using [Cmd::parse_until_sub_cmd]:
 //!
-//! ```
+//! ```rust
 //! use cliargs::Cmd;
 //! use cliargs::errors::InvalidOption;
 //!