refactor: align custom font class with resource pack definition

[theEvilReaper]

Proposed changes

The original idea was to have a font record which represents a font entry from a resource pack. This also comes with a key which represents the entry itself. Unfortunately the idea with the key makes it less a data representation. So this pull request overhauls the structure to have a easy data representation of a font entry.

This comes with the advantage that each developer can do their own mapping to have Key -> Font.

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

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• I have read the CONTRIBUTING.md
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)