fix copying from emacs to local clipboard

apparently with tmux 3.3 if you run emacs inside tmux locally on the
machine you need to enable passthrough. kinda weird?

see https://github.com/spudlyo/clipetty/issues/25#issuecomment-1327472790

.tmux.conf

@@ -21,6 +21,7 @@ bind . attach-session -t . -c '#{pane_current_path}'
 
 set -g mouse on
 set -g allow-rename off
+set -g allow-passthrough on
 set -g history-limit 50000
 
 # Allow Spacemacs to correctly show colours