feat(tazjin/rlox): Support local variables

WIP

Change-Id: I78fbc885faaac165c380cbd9aa98b4b64a9b8274
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3685
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>

users/tazjin/rlox/src/bytecode/opcode.rs

@@ -34,4 +34,6 @@ pub enum OpCode {
     OpDefineGlobal(usize),
     OpGetGlobal(usize),
     OpSetGlobal(usize),
+    OpGetLocal(usize),
+    OpSetLocal(usize),
 }