added grammar files

src/main.rs

@@ -1,5 +1,11 @@
+use lalrpop_util::lalrpop_mod;
+
 mod ast;
 mod optimising;
+mod tests;
+
+lalrpop_mod!(pub literals);
+lalrpop_mod!(pub expressions);
 
 fn main() {
     println!("Hello, world!");