HGSS Missing PokeWalker Encounters

The API is currently missing the PokeWalker encounters from the HGSS companion accessory.

I think this should be supported, first of all, and I would do it in two separate PRs:

1. All regular locations
2. All event locations

The PokeWalker has its own sub-locations, but whenever a Pokemon caught in it is shown in-game, it just says "pokewalker".

I would propose we add 6 things to include the PokeWalker:

1. PokeWalker Location
2. Location areas for each PokeWalker area, tied to the pokewalker location: https://bulbapedia.bulbagarden.net/wiki/Pok%C3%A9walker#Areas
3. Encounter Method called Pokewalker Transfer
4. Encounter condition called "steps" and show the minimum number of steps you need to walk to find that Pokemon.
5. Encounter condition called "group x" to note which group the pokemon is a part of. Because some mons are mutually exclusive.
6. Encounter condition called "region"

On note 6. The "special" areas include event only areas, and some are japan only. Those I would set those areas to the encounter condition called: region-japan, indicating you need a japanese pokewalker.

Start by reviewing the existing HGSS location, encounter method, and encounter condition data, then compare it with the linked Bulbapedia Pokéwalker areas. Done means the regular Pokéwalker locations, areas, transfer method, and steps, group, and region conditions are represented consistently in the API.