crossterm: Stop mouse mode and show cursor at finish (#400)
crossterm: Stop mouse mode and show cursor at finish (#400)

Something is wrong at the moment when finishing up, when
the crossterm backend is used.

The terminal is left in a strange state: the previous contents of the
terminal (as before the program) are visible, however the cursor is
invisible (and reset to the top left), and clicking the mouse spams
escape codes.

For some reason the `execute!` block in `finish` is failing. But it
doesn't seem to be necessary: crossterm already restores the alternative
screen at shutdown, which also restores the original cursor position and
attributes.

Do make sure that mouse mode is stopped and that the cursor is visible.
Gyscos/Cursive