Extend data manager to read Pokemon Showdown! files

[mirekdlugosz]

Pokémon Showdown! is exhaustive source of information about Pokémon games since gen III. It has two advantages over veekun:

• Bigger community, meaning faster support for new games
• Movesets include event moves

It would be great if our data-manager could support Pokémon Showdown! files as data sources.

For starters, it could use Pokémon Showdown! as only source of data. Eventually it should be able to read veekun data and add missing pieces from Pokémon Showdown!.

Pokémon Showdown! data is held in JavaScript arrays that are not readable by standard JSON parsers. It must be first transformed to JSON. See data-manager/data-source/js-to-json.sh in ac3d664 for one way to transform it.

Both Pokémon and move names differ a little between veekun and Pokémon Showdown!. Some way to transform names from one space to another must be found. Similar problem must be solved as part of Issue #9. It would be really cool if we could find a way to solve both without code duplication.

[mirekdlugosz]

This got broken down into:

• Create script converting Pokémon Showdown! files to portable JSON #25
• Basic Pokémon Showdown! pokedex reader #26
• Translation layer for veekun and Showdown in pokedexreader #27
• Support games / generations in Pokemon Showdown pokedexreader #28
• Add edge-cases support in Pokemon Showdown pokedex reader #29

[mirekdlugosz]

Implemented while working on "Prepare for Sword and Shield".