ast: Add use, tackle remaining low-hanging fruit

src/token.rs

@@ -82,12 +82,15 @@ pub enum TKind {
     Macro,
     Match,
     Module,
+    Mut,
     Or,
     Public,
     Return,
     Static,
     Struct,
     True,
+    Type,
+    Use,
     While,
 
     Identifier, // or Keyword