Introduce `.cancel` event that is fired when the user sends EOF
in *non raw mode* renderings. The event `.line` now sends the
entire line (even if larger than the internal buffer) but requires
now an `Allocator`.
The end of the `.line` event received contents is highlighted by a trailing newline
(which cannot occur before, as that triggers the line event itself).
Add signal handler for SIGCONT which forces a `.resize` event that should re-draw the
contents after continuing a suspended application (i.e. ctrl+z followed by `fg`).
Setting the cursor with the `Direct` handler will cause the rendering
to halt at that point and leave the cursor at point.
Due to not enabling *raw mode* with the newly introduced `App.start`
configuration options corresponding inputs are only visible to `zterm`
once the input has been completed with a newline. With this it is not
necessary for the renderer to know nothing more than the width of the
terminal (which is implied through the `Container` sizes). Making it
very trivial to implement.
Handle inputs as per usual (which however is a bit weak, is it goes through
key by key and not the entire line), batch all events such that all events
are handled before the next frame is rendered. For this the `App.start`
function needs to become configurable, such that it changes the termios as
configured (hence it is currently all commented out for testing).
A corresponding example has been added, which is very minimalistic as of now,
but will add further functionality to test the corresponding workflow that is
usual in `zterm` such that it in the best case only a swap in the renderer to
switch from alternate mode drawing to direct drawing.
