Add skin tone and hair color options for Mulberry symbols

[jacobmcgowan]

Similar to #1835

Benefit

Allowing users to select a skin tone and hair color for symbols that more closely resemble them would help make boards feel more personal.

Update Mulberry symbols

The latest version of the Mulberry symbols include classes that make it easier to find and edit paths such as aac-skin-fill and aac-hair-fill. Using these new classes, we can generate variations with different skin tones and hair colors similar to what ARASAAC provides or potentially edit symbols during runtime.

Generate variations

I wrote a tool, svg-quick-edit, to quickly edit paths in SVG files and used this to generate variations of the base symbols in commit f13bfa6 in my fork of CBoard using this script which includes the same HEX code variations that ARASAAC uses.

One problem with this approach is that it increases the size of the Mulberry symbols folder from 39 MB to 288 MB. If this is acceptable, then I can continue working on this branch; otherwise, then it may be better to edit the SVG during runtime.

[jacobmcgowan]

I have updated svg-quick-edit to ensure that it only creates variation files for each change that it makes. For example, absent.svg includes skin but not hair so it only saves skin tone variations such as absent_skin-a65c17.svg.

With this change in commit 4634f77 on my fork I was able to reduce the Mulberry symbols folder to 135 MB with skin tone and hair color variations.