feat(tazjin/rlox): Implement simple arithmetic operators

Change-Id: I9873bcd281053f4e9820a5119f5992a0b8cb8cfc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2417
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>

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

@@ -5,4 +5,13 @@ pub enum OpCode {
 
     /// Return from the current function.
     OpReturn,
+
+    /// Unary negation
+    OpNegate,
+
+    // Arithmetic operators
+    OpAdd,
+    OpSubtract,
+    OpMultiply,
+    OpDivide,
 }