[ubuntu22.04] Fcitx5 does not work on snap apps, PR included

Hi all,

I have recently installed Fcitx5 on Ubuntu 22.04, but I couldn’t use any input method on Snap applications (Firefox, Vscode, slack, etc.) Perhaps it is because Fcitx5 is a new, different IM with its frontend package separated (fcitx5-frontend-*). Has anyone noticed the same issue?

I propose a PR to solve the problem but haven’t tested it so far. I am not familiar with snap build. https://github.com/ubuntu/snapcraft-desktop-helpers/pull/230