Unfortunately the formspec seems not to be properly updated when
unchecking a checkbox, even if fields are sent and thus the formspec
action should be triggered. This causes unselecting the currently
selected timer type to be unselected when uinselecting it – instead of
updating the formspec and show the selected option again.
This is just a “visual glitch” and does not affect the timer
functionality. When re-opening the timer window the type is selected
correctly again.
addresses https://gitlab.com/4w/mtimer/-/issues/11
Since the custom timer formspec is fairly complex (and will be a bit
more complex in the future) the best thing is splitting it off from the
other formspec definitions.
