feat(tazjin/rlox): Parse function declarations

Change-Id: I1db4316563827976e5233dc7a626968f80b992ef
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2390
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

users/tazjin/rlox/src/interpreter.rs

@@ -208,6 +208,7 @@ impl Interpreter {
             Statement::Block(block) => return self.interpret_block(block),
             Statement::If(if_stmt) => return self.interpret_if(if_stmt),
             Statement::While(while_stmt) => return self.interpret_while(while_stmt),
+            Statement::Function(_) => unimplemented!(),
         };
 
         Ok(value)