Add source files: main.rs, lib.rs, cli.rs, error.rs

src/main.rs

@@ -0,0 +1,16 @@
+use std::process;
+use git_commit_prefix_gen::cli::{CliArgs, run};
+
+fn main() {
+    let args = CliArgs::parse();
+
+    match run(&args) {
+        Ok(exit_code) => {
+            process::exit(exit_code);
+        }
+        Err(e) => {
+            eprintln!("Error: {}", e);
+            process::exit(e.exit_code());
+        }
+    }
+}