feat(mods/Monster_Girls,content): Add Kitsunes to Monster Girls Mutations

[RobbieNeko]

Checklist

Required

• I wrote the PR title in conventional commit format.
• I ran the code formatter.
• I linked any relevant issues using github keyword syntax so it can be closed automatically.
• I have committed my changes to new branch that isn't main so it won't cause conflict when updating main branch later.

Purpose of change

More monster girl mutation paths is better so as to avoid overly narrowing player choice.

Kitsunes seemed like a fitting choice for a sort-of beast equivalent, being a bit of a mix between dogs and cats.

Describe the solution

Adds the Kitsune mutation tree, basing them off of the existing Beast tree (and a little bit of Feline)

Describe alternatives you've considered

• Implode
• See if a mod has done a good Kitsune path and politely ask to base the monster girl one off of theirs

I tried looking for Shard's one, but couldn't find it (and by the sounds of things, that one got left in WIP hell)

Testing

It loads on my machine, and the linter didn't complain

Additional context

Kitsune-Neko alliance goes hard

I should probably make proper orange ears / tail in the future. (even if it's just recolors of what I'm using right now)