chore(tazjin/rlox): Add some old code example files

Change-Id: I484b11069286ea2277e9e158fa5c3bd34f84c89e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3464
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>

users/tazjin/rlox/examples/slow.lox

@@ -0,0 +1,9 @@
+fun fib(n) {
+  if (n < 2) return n;
+  return fib(n - 1) + fib(n - 2);
+}
+
+var before = clock();
+print fib(40);
+var after = clock();
+print after - before;