Make bench_shells can take optional arguments to delegrate hyperfine

Such as `bench_shell --export-markdown -`

pkgs/bench_shells/bench_shells.bash

@@ -1,5 +1,5 @@
 # zsh should be first, because it often makes much slower with the completion
-hyperfine --warmup 1 --runs 3 --shell none \
+hyperfine --warmup 1 --runs 3 --shell none "$@" \
 	'zsh --interactive -c exit' \
 	'zsh --no-rcs --interactive -c exit' \
 	'bash -i -c exit' \