Ignore ascent metric in MonoFont conversion

[rfuest]

This PR changes the mono font conversion to only rely on the glyph bounding boxes to ensure that glyphs aren't cut off or overlap. The font bounding box and ascent metrics are ignored, instead a union of all included glyph bounding boxes is used.

[matze]

Works fine as well, thank you!

[rfuest]

Thanks for testing.

I've updated the PR to fix some edge cases and to add a setting to change how the glyphs of a proportional font are aligned in the larger monospace bounding box.

Left aligned:

Center aligned (the new default):

I think the more even spacing of the characters, especially narrow ones like I and J, look better in the centered version.

[matze]

I think the more even spacing of the characters, especially narrow ones like I and J, look better in the centered version.

Absolutely, I noticed that as well. Thanks for looking into this closer.