Consider a fcitx5 extension

[pythonbrad]

fcitx5 has been ported to Android, macOS and web so if we want an easier way to let engine cross-platform, without a need to maintain all the different frontends, that's the chance.

[pythonbrad]

This is will require to implement

• Is there a need for a C library? #260

Before jump on it, test the fcitx5 implementation.

[pythonbrad]

For the fcitx5, can check

https://github.com/OpenBangla/riti/

https://github.com/naokiri/cskk/blob/master/cskk/src/capi.rs