fix: uui-combobox click to close by adding toggle

[enkelmedia]

Fixes this: #668 so that clicking the arrow will toggle the list and not "just" open it.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

• New feature (non-breaking change which adds functionality)

• Breaking change (fix or feature that would cause existing functionality to change)

• Chore (minor updates related to the tooling or maintenance of the repository, does not impact compiled assets)

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• I have read the CONTRIBUTING document.

• I have added tests to cover my changes.

[github-actions]

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[iOvergaard]

LGTM. Thanks!