Expanded language support

What's new:

• files are saved in .txt format by default now
• you can still save them in an arbitrary format or with none at all if you want to
• added support for pretty much all alphabets that exist around the world
  • we already had good support for Cyrillic, Latin Extended and Japanese character sets before this
  • now we support almost everything there is with a few rare exceptions you likely wont notice

Known issues:

• we do not have Right to Left text support yet, but...
• that is a feature that Godot 4.0 is said to have. It will release in the near future, we will add this feature once the new version of the engine is available
• we are aware that copy-pasting text written from right to left results in it getting flipped, this is a problem that is common for many applications, we will try to fix this issue in the future when full RtoL support comes with Godot 4.0
• some beefy characters like emoji and Egyptian hieroglyphics are only displayed on the Linux version, this is a bug in the engine and we have no fix for it at the moment