fish: Set environment for non systemd user services/applications

Environment variables in environment.d directory only affects the users
systemd unit. For example, while these environment variables are set in
tmux which we start via systemd, these are not set when we open terminal
outside of tmux.

See related,
https://github.com/systemd/systemd/issues/7641

fish/.config/fish/conf.d/setup.fish

@@ -57,6 +57,8 @@ function __fish_setup_on_tty_login --description "Set up environment on tty logi
     # Required for all environment variables to be set correctly, especially
     # in tmux session service.
     dbus-update-activation-environment --systemd --all
+
+    export $(/usr/lib/systemd/user-environment-generators/30-systemd-environment-d-generator)
 end
 
 # Instead of tty check, we would have liked to do this using status is-login