Make Ctrl+Shift+E (emoji) and Ctrl+Shift+U (Unicode) user-configurable
U are used by
GtkIMContextSimple for entering emoji and unicode.
These key combinations are already used by many other software packages and web sites, but become useless as they are intercepted by Gnome.
Users should be able to set other combinations as the "Enter Emoji/Unicode" combination (for example,
E...), ideally via a dotfile.