[Bug] Custom CSS Editor can not Handling multibyte characters correctly

[TsubasaKawajiri]

Describe the Bug
Custom CSS Editor panic caused by multibyte characters.

To Reproduce

1. Input any multibyte characters(e.g: emoji(🦄) and Japanese(あ)) to Custom CSS Editor.
2. Input any characters.
3. Characters appear to Custom CSS Editor more than input.
   ex; Copy & Paste is more causes strange behavior.

Expected Behavior
doesn't panic by multibyte characters.

Discord Version
Stable

Additional Context
This bug is not fatal. because in edit CSS usually, not used multibyte characters.

[TsubasaKawajiri]

I'm examined this problem.

• checked multibyte characters in ACE live demo(https://ace.c9.io/build/kitchen-sink.html).
  • doesn't reproduced.
• change Font by any Better Discord Themes.
  • reproduced and more strange behavior.
• and found some problem issue(Cursor doesn’t work in multibyte text ajaxorg/ace#1594) at ACE issues.
  • found old version ACE live demo(https://brionv.com/misc/demo/ace/build/kitchen-sink.html) at this issue. and it's reproduced this problem.
• found character widths issue(Support varying character widths  ajaxorg/ace#460)

by these, this problem is depend on Font and ACE version, not Better Discord problem I think.

so can't fix this on Better Discord because ACE is not exist on Better Discord context.

[TsubasaKawajiri]

If there aren't any problems, please close this.

[TsubasaKawajiri]

if install ACE on Better Discord context, may fix this problem.
but it will be complicated dependency.

[TsubasaKawajiri]

thank you fix this!