Using regex in hunspell affix file

The regular expression is used very nicely in this example.

SFX j a âed tha
SFX j a âed cha
SFX j a aed [^tc]ha

https://github.com/fin-w/LibreOffice-Geiriadur-Cymraeg-Welsh-Dictionary/blob/main/dictionaries/cy_GB.aff