UDP External Tileset Update

[chaosvolt]

Summary

SUMMARY: Interface "Update external tileset"

Purpose of change

A belated update to add some more sprites for stuff specific to BN, as requested by Scarf.

Closes #3231

Describe the solution

Added sprites for:

1. Welded shield, belatedly.
2. Buckler, direct port from Medieval Mod Reborn mod tileset.
3. The new battle masks.
4. Bronze arm guards.

MISC: Fixed plural of bronze arm guards.

Describe alternatives you've considered

1. Spriting spiked shields too, maybe if I ever figure out how to make spiked armor actually mean something statwise, weh.
2. Figuring out how to mainline the anime ears mod for the sake of feat: animal ears are cute #3230

Testing

1. Checked affected tile config for syntax and lint errrors.
2. Load-tested in compiled build.

Additional context

[scarf005]

[chaosvolt]

Arm guards and shields both being strapped layer is amusing.