Strips Ligatures, Substitions, and Pairwise Positions

[solonovamax]

When fonts are processed with this, it seems that the following things are stripped:

• Ligatures
• Substitutions (including alt. substitutions)
• Pairwise positioning
• & possibly more

This even happens when converting (for example) woff2 -> woff2.

Related: #57 (to my understanding, that issue is specifically about icon fonts)

Reproducing:

1. open font with ligatures/substitutions/positioning in fontforge, and identify a character with ligatures/substitutions/positioning
2. process font with library
3. open font in fontforge, and observe that the ligatures/substitutions/positioning on the previously identified character are now gone

I was personally able to reproduce this with Fira Sans, Fira Code, and TeX Gyre Termes.