Add Simplified Chinese localization

[pcs801]

Summary

Simplified Chinese localization for Boss Rush Wave Counter:

• Translated all Mod Config Menu options and the "Edit Mode" indicator into Simplified Chinese
• Bundled a CJK pixel font (fusion-pixel, OFL-licensed) under resources/font/fusion-pixel/ so Chinese text renders correctly
• Switched text rendering to the UTF-8 draw APIs (DrawStringScaledUTF8 / GetStringWidthUTF8), required for Chinese text on the NG engine
• The wave counter digits keep using the original terminus font, so the HUD appearance is unchanged

Notes

• The CJK font is required for the Chinese text to display correctly
• No gameplay changes
• The mod name and MCM category name are kept in English so the official mod identity stays unchanged

[AaronCohen21]

To my understanding this change was supposed to add a simplified Chinese translation to the MCM settings page. Instead, this PR replaces all text with simplified Chinese.

In order to accommodate both languages an i18n library (e.g. https://github.com/kikito/i18n.lua) should be imported as a dependency, and the code will need to be refactored to accommodate this change.

Im not too sure about what the best lua package manager out there is, but the library should be added as a dependency through some system so it can be easy to upgrade in the future if need be.

I'm happy to add these changes myself, but might not get to it for a little bit.

[pcs801]

That approach sounds good to me — thanks for offering to take care of the i18n implementation. I'll leave that to you.
If it's helpful, I can provide the Simplified Chinese translation strings whenever you need them. Let me know if there's anything else you need from my side.