Add amenity field on structured search form

[mtmail]

Related @osm-search/Nominatim#3054

[0xSaksham]

@mtmail I can work on this issue. Is there anything I should know about first?

[mtmail]

@0xSaksham

Thank you for the offer.

https://nominatim.openstreetmap.org/ui/search.html is an example installation of the nominatim-ui. You can run it on your local machine easily. yarn dev will auto-reload the pages after every change, see the CONTRIBUTE.md for instructions.

The Nominatim backend API search has two query modes: "simple" (also called "free form") and "structured".
https://nominatim.org/release-docs/latest/api/Search/#endpoint

On the nominatim-ui frontend when you click "Structured" on the /search.html page you will see a list of fields, e.g city, state, country.

Goal is to add another field called "amenity". A user should be able to search for amenity=restaurant, city=paris, country=france and receive a list of restaurants as result.

The relevant code is in /src/components/SearchSection.svelte. Since it's the 7th field a lot can probably be copied from the other 6.

The new feature won't need a test.