Implement a schema for the measurement field

[k-yle]

Closes #15

Here's a concrete proposal for the measurement field. Every measurement field needs to define dimension, usage, and units. See discussion in #15.

For units, the keys are the IDs used by CLDR. The value(s) are the the units that are used in the OSM tag.

{
    "key": "maxspeed",
    "label": "Speed Limit",
    "placeholder": "40, 50, 60...",

    "type": "measurement",
    "measurement": {
        "dimension": "speed",
        "usage": "default",
        "units": {
            "kilometer-per-hour": [""],
            "mile-per-hour": ["mph"],
            "knot": ["kt", "kn"]
        }
    }
}

This implementation is a bit complicated because:

• we want the json schema to validate that dimension, usage, and the keys of units are valid, using cldr-core
• when fetching translations from transifex, we need to merge the translations with CLDR's translations, for the units that we use, using cldr-units-full.

The generated dist/translations/*.json files now contain a new property called units:

  // es.min.json
  {
    "presets": { … },
+   "units": {
+     "speed": {
+       "kilometer-per-hour": { "long": "kilómetros por hora",  "narrow": "km/h" },
+       "mile-per-hour": { "long": "millas por hora", "narrow": "mi/h" },
+       "knot": { "long": "nudos", "narrow": "kn" }
+     }
+   }
  }

The PR does not implement any logic to extract the default values per region, because it's not yet clear where this data should be stored.

[k-yle]

auto-complete & validation works nicely, at the expense of complicating the code in this package:

Screen.Recording.2025-05-06.at.20.39.47.mov

[k-yle]

conflicts resolved