Take font widths from the project instead of a json file.

[Jaizu]

Keeping that file updated when you have custom characters or changed font-size is usually a pain in the ass, specially when that file doesnt only contain character widths but also other values like numLines.

[huderlem]

For clarity, this is referring to the font widths defined in the decomps. (e.g. from fonts.c). This would currently require parsing both charmap.txt and fonts.c, which seems rather brittle. If the decomps had a normalized data structure (e.g. a JSON file), this would be more realistic to support.