Refactor: Migrate to clap for CLI argument parsing

The project now uses the `clap` crate for handling command-line
arguments, replacing the previous manual parsing approach. This includes
adding `clap` as a dependency and creating a `Cli` struct to define the
command-line interface. The `main` function has been updated to parse
these arguments and handle file input or direct script evaluation.

src/main.rs

@@ -1,9 +1,5 @@
 use eframe::egui;
-use crate::ast::environment::Environment;
-
-pub mod ast;
-#[cfg(test)]
-mod integration_test;
+use myc::ast::environment::Environment;
 
 fn main() -> eframe::Result {
     let options = eframe::NativeOptions {