Implement language switching in URL querystring

[ZeLonewolf]

Depends on #19

A key feature of vector tiles is the ability to switch languages for name labels. OpenMapTiles provides name:xx tags wherever a name tag is available. Proposed is that the following parameters can be parsed from the querystring:

*lang0=xx - use name:xx tag for name features
*langN=xx - use name:xx as a fallback language if the lang0 language is not available. N is numbered from 1 and counting up

If none of the specified languages or fallback languages are set, this will default to one of the standard name values (one of name, name_int, or name_latin).

In javascript, a JSON fragment will need to be generated which creates a case statement to switch the specified language names, which is then inserted into the appropriate locations in the style JSON variables.

[ZeLonewolf]

The following library may be of use:
https://github.com/klokantech/openmaptiles-language

[1ec5]

The following library may be of use: https://github.com/klokantech/openmaptiles-language

This script predates expressions and uses the deprecated string interpolation syntax, so it’s incompatible with this project. It also isn’t distributed as an NPM package. There is a compatible Mapbox GL JS library for localizing labels. However, I don’t think a library is necessary at all. Unlike most styles that are distributed in static JSON format, Americana is built at runtime in JavaScript, giving us the ability to inject environment variables like the language as we build each layer. #578 implements this approach without needing to hard-code a single name:* field.

#578 relies on user preferences, but I agree that it would be handy to be able to set the language inside the URL. There are two typical approaches to implementing a URL-based language switch:

• A ?language= query parameter would be ideal. I think GitHub Pages supports query parameters just fine, but when running npm start, appending any query parameter currently results in a 404. We would need Accept query string in request nativew/serve#8 to land before taking this approach.
• A #language= hash “parameter” is a common alternative. It has the benefit of implying that the user can change the language without reloading the page, which would be feasible: Use user-preferred language in labels #578 (comment). Unfortunately, we’re currently using the basic hash y/x/z hash format, which leaves no room for additional parameters. The fix is simply to set hash to the string map here: https://github.com/ZeLonewolf/openstreetmap-americana/blob/0ff8c2434ab61496b2548687ed1cc7436179bfd3/src/americana.js#L286 This would be consistent with the rest of the OSM ecosystem, including osm.org and iD. However, this would break all existing links to specific locations in Americana unless we add a compatibility shim.

[jleedev]

Can also switch to esbuild's serve api.