Update formula schema: Add font category labels

[ronaldtse]

Glyph type (can we detect, or need to assign?):

• Serif: Traditional fonts with small lines (serifs) at the ends of strokes. (have to detect via software like OpenCV: https://stackoverflow.com/questions/64948930/how-might-i-detect-serif-and-sans-serif-fonts-in-python-opencv)
• Sans Serif: Modern, clean fonts without serifs. (as above)
• Script: Fluid, handwritten-style fonts. (cannot autodetect?)
• Display: High-impact, decorative fonts for headlines. (cannot autodetect?)
• Monospaced: Fixed-width characters, often used for coding. (can detect by checking if glyph width is identical)
• Handwritten: Informal, script-like styles. (cannot autodetect?)

Font format available (not considering transcoding):

• TTF, OTF, etc. (this info is already in the Formula)

Features (can detect):

• Ligatures (need Fontisan to support)
• Variable fonts and axes (supported by Fontisan)
• language set support (need Fontisan to support)
• unicode plane support (need Fontisan to support)
• weights available (need to detect from non-variable fonts)
• "style categorization"? e.g. italics, bold, heavy, medium, etc. (this may require labeling enumeration for per-style font files)