Obfuscated Text Improver

Fixes MC-277733 by restricting characters that can be chosen when rendering obfuscated text.

With mod:</br> <img src="https://cdn.modrinth.com/data/cached_images/5a5df8386fddd7b71d6fda744c8a708e841934d4.png" alt="Obfuscated text in a book with mod" width="300">

Without mod:</br> <img src="https://cdn.modrinth.com/data/cached_images/a0e8bb87ad838f85d4e8adc931267abd1bee5c8c.png" alt="Obfuscated text in a book without mod" width="300"> <img src="https://cdn.modrinth.com/data/cached_images/f1081edbf5c2380371b59482ff496bff19b3afa6.png" alt="165 files of font atlas" width="364">