fcitx5-lua provides Lua support for fcitx5.
It tries to support lua in fcitx in two ways:

1. An addon loader for lua, which supports Type=Lua addon.
2, The googlepinyin api, which is provided by imeapi addon.

You may put your lua file under
$HOME/.local/share/fcitx5/lua/imeapi/extensions to make the addon
find your scripts.