Improve Black Font Contours

[RobertWinslow]

This is a followup to some of the side-discussion from #93

After #422, the quality of the fonts is vastly improved. And the black font in particular now uses a near-universally supported format. Fantastic!

But the fonts still are not perfect. I've generated a table for visually inspecting all the glyphs. The comparison table can be found here: https://robertwinslow.github.io/openmoji/font/black-font-comparison-table

Preview:

The first column contains the 72x72 PNG image of the glyph. The second column displays the character using the official black glyf font generated using NanoEmoji. The third column displays the glyph using an alternate version of the font, built using FontForge's (v20220308) importOutlines scripting functionality.

Here's an (atypical but striking) example demonstrating that neither contour generation method has results exactly as desired:

In some cases, these imperfect contours may be the unavoidable result of bugs in the tools used to create them. In other cases, they may indicate fixable problems in the source SVG files.

[RobertWinslow]

Some additional links:

This branch has the html comparison tables I generated, as well as the scripts I used to generate them: https://github.com/RobertWinslow/openmoji/tree/black-font-comparison-ff-ne

I also generated tables for inspecting individual fonts. See EG: https://robertwinslow.github.io/openmoji/font/OpenMoji-color-glyf_colr_0/font-comparison-table.html

The color fonts generated by NanoEmoji seem to have very few flaws.

[b-g]

Very nice comparison table! Thanks! Just as usual there is not a lot of glory in fixing these nitty gritty issues. Not sure whether this will happen soon ...