[dev][st] Solution: UTF-8 needs IBus!

[Robert Winkler]

To make a long story short: The input of UTF-8 characters with st needs
an IBus daemon (standard on Gnome, but not on other window managers such
as Plasma, dwm, ..).

I added to ~/.config/autostart:

`Ibus-Daemon.desktop`

~~~
[Desktop Entry]
Name=IBus Daemon
Type=Application
Exec=ibus-daemon -drx
Terminal=false
~~~

Thanks for all your ideas!