feat(web): long press on suggestion to select affixes

**Is your feature request related to a problem? Please describe.**

From [Luke](https://community.software.sil.org/t/keyman-roadmap-march-2020/822/29):

> Maybe a long press on a word suggest or on a root suggestion that could bring up derivations of words and let the user choose the word they want could speed up typing of languages where there is quite a bit of affixation. When all your verbs start with a few prefixes, but the middle of the word is what makes the difference, it will be hard for prediction software to be useful until after 3 or 4 letters are already typed.

**Describe the solution you'd like**

We'd need to get the affix data and link it to the wordlist somehow and its common wordforms (word + affixes). Then, we could enable a long press on a suggestion to see its common affixes.