[Sprite] Galarian Bird Variants to JSON

[pom-eranian]

4144 Articuno
4145 Zapdos
4146 Moltres

What are the changes the user will see?

Backsprite for g. moltres variants will show up. (reported by different people)
The colors for any sprite of the same variant are exactly the same

Why am I making these changes?

• Part of asset cleanup.
• Fixes visual bug for galarian moltres
• just because, i guess.

What are the changes from a developer perspective?

Created palette json files for front, back and exp front
Edited _masterlist.json to use a color swap instead of images on these pokemon.

Screenshots/Videos: the garbled ones are 'animated' :/

forgot one but if the variants work, the base works.

How to test the changes?

set sprites to mixed animated
set species to each of the following: 4144, 4145, 4146
set values for shiny and variant as needed

Checklist

• I'm using beta as my base branch
• There is no overlap with another PR?
• The PR is self-contained and cannot be split into smaller PRs?
• Have I provided a clear explanation of the changes?
  - [ ] Have I considered writing automated tests for the issue?
  - [ ] If I have text, did I make it translatable and add a key in the English locale file(s)?
• Have I tested the changes (manually)?
  • Are all unit tests still passing? (npm run test)
• Are the changes visual?
  • Have I provided screenshots/videos of the changes?