Called when a terminal is about to be placed in the shell.
The handler may take ownership of the terminal (e.g. add it to a custom container)
by returning true. In that case, the default shell placement will be skipped.
The terminal widget to be placed.
Optionaloptions: WidgetOpenerOptionsThe opener options, if any.
true if this handler claimed the terminal, false or undefined otherwise.
The priority of this handler. Higher values are consulted first. Defaults to
0if not specified.