consider adding diphthongs and clusters again, due to irregularities in NAPA

[LinguList]

napa writes some sounds like ᵏp which is our kp, etc. If we want to handle those consistently, we need to allow to define diphthongs in addition to consonants, vowels, and tones. We can either ignore these, or we have to modify the framework.

[LinguList]

I'll ignore it for the time being. We can think of adding this in the future. For the time being, when dealing with datasets in this style, we can use orthography profiles or similar.