Support completion of dirs

[reubeno]

Extend previous filename completion to support filtering on dirs.

[github-actions]

Test Results

344 tests   329 ✅  2m 14s ⏱️
 56 suites   15 💤
  8 files      0 ❌

Results for commit b00d49a.

[github-actions]

Performance Benchmark Report

Benchmark name	Baseline (ns)	Test/PR (ns)	Delta (ns)	Delta %
expand_one_string	3318 ns	3319 ns	+1 ns	🟠 +0.03%
instantiate_shell	52387 ns	52096 ns	-291 ns	🟢 -0.56%
instantiate_shell_with_init_scripts	47414740 ns	47162304 ns	-252436 ns	🟢 -0.53%
parse_bash_completion	6640516 ns	6621020 ns	-19496 ns	🟢 -0.29%
parse_sample_script	10818 ns	10900 ns	+82 ns	🟠 +0.76%
run_echo_builtin_command	90877 ns	90908 ns	+31 ns	🟠 +0.03%
run_one_builtin_command	108174 ns	108042 ns	-132 ns	🟢 -0.12%
run_one_external_command	1789760 ns	1883961 ns	+94201 ns	🟠 +5.26%
run_one_external_command_directly	1013050 ns	1025649 ns	+12599 ns	🟠 +1.24%

Code Coverage Report

Package	Base Coverage	New Coverage	Difference
cli.src	🟠 73.95%	🟠 73.95%	⚪ 0%
interactive-shell.src	🟢 75.88%	🟢 75.88%	⚪ 0%
parser.src	🟢 85.86%	🟢 85.86%	⚪ 0%
shell.src	🟢 79.93%	🟢 79.98%	🟢 0.05%
shell.src.builtins	🟠 64.03%	🟠 64.03%	⚪ 0%
Overall Coverage	🟢 77.99%	🟢 78.02%	🟢 0.03%

Minimum allowed coverage is 0%, this run produced 78.02%