[accessibility] Screen reader-friendly results list

[Malvoz]

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It is currently not conveyed to screen reader users which results are available after typing text in the search input.

Please consider following the ARIA Authoring Best Practices for the Combo Box design pattern.

Potentially helpful resources:

• role="combobox" definition
• MDN docs: role="combobox"
• Leaflet guide to accessibility: Test your maps
• Leaflet Plugin Authoring Guide: Content Accessibility