Add mypy (#224)

scripts/benchmark.py

@@ -6,6 +6,7 @@ import subprocess
 
 from itertools import islice
 from pathlib import Path
+from typing import Iterable
 
 from typer import run
 
@@ -15,7 +16,7 @@ def main(
 ):
     path = Path("benchmark")
 
-    folders = path.iterdir()
+    folders: Iterable[Path] = path.iterdir()
 
     if n_benchmarks:
         folders = islice(folders, n_benchmarks)