Add onShouldExpand and onShouldCollapse callbacks

[i-like-robots]

The adds onShouldExpand and onShouldCollapse callback props which enable an implementor to override the default behavior of the listbox - either to forcing the listbox to remain collapsed or remain expanded.

For example to force the listbox to remain collapsed when the input value is empty:

function onShouldExpand(value) {
  return value.length > 1
}

Resolves #15

[github-actions[bot]]

Pull Request Test Coverage Report for Build 5408944716

• 24 of 24 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 99.222%

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Totals
Change from base Build 5405463548:	0.01%
Covered Lines:	1444
Relevant Lines:	1451

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 5408944716

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 24 of 24 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 99.222%

---

Totals
Change from base Build 5405463548:	0.01%
Covered Lines:	1444
Relevant Lines:	1451

---

💛 - Coveralls