feat: add introspection benchmarks

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #9 feat/introspection-benches (8f23362) will create unknown performance changes.

Congrats! CodSpeed is installed 🎉

🆕 5 new benchmarks were detected.

You will start to see performance impacts in the reports once the benchmarks are run from your default branch.

Detected benchmarks

- `test_iterative_fibo_10` (31.8 µs) - `test_recursive_fibo_10` (325.9 µs) - `test_recursive_fibo_20` (38.2 ms) - `test_recursive_cached_fibo_10` (86.6 µs) - `test_recursive_cached_fibo_100` (678.3 µs)