Exporting braille characters results in text filled with question marks ("?")

[Mumberthrax]

Describe the bug
A clear and concise description of what the bug is.

Clicking "export to file" while reading a book with certain unicode characters, like the braille characters produced by https://github.com/Equbuxu/BrailleBooks, produces a text file with questions marks in place of those unicode characters.

To Reproduce
Steps to reproduce the behavior:

1. Paste "⣿⣿⣿⣿⣿" into a book&quill in Minecraft with Textbook mod enabled.
2. Click "Sign", enter a title, click "sign and close"
3. Right click with book in hand, click "export to file", and save as a new file someplace.
4. Open the newly created file in a text editor and see "?????"
5. Open a new book&quill in Minecraft and click "import from file"
6. select the newly created file
7. Observe "?????" instead of "⣿⣿⣿⣿⣿"

Logs/Screenshots/Videos
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Versions (please complete the following information, do NOT say "latest"):

• Minecraft: 1.17.1
• Mod Version: 2.0.0
• Fabric API: 0.11.6