add argument parser + parse config arg, Fixes #5

src/main.rs

@@ -1,11 +1,19 @@
+use clap::{command, Parser};
 use risp::law::Law;
 
+#[derive(Parser, Debug)]
+#[command(version, about, long_about = None)]
+struct Args {
+    /// Path to the config of a law text
+    #[arg(short, long)]
+    config: String,
+}
+
 fn main() {
     env_logger::init();
 
-    let config_path = "./data/configs/stgb.toml";
-
-    let law = Law::from_config(config_path).unwrap();
+    let args = Args::parse();
+    let law = Law::from_config(&args.config).unwrap();
 
     law.to_md();
 }