fullscreen_bg defaults to black

Per conversation at PR #1147 with @kilpilainen

Update README.md

Correct description of default background color

float sub-windows matching a rule

Currently when a rule that doesn't make windows floating matches, even
sub-windows of float type get tiled rather than just the main window.
This is inconsistent with dwm and other compositors. Fix this by making
these windows floating after applying rules.

Fixes #1142.

document status output

Use a subsection for mouse commands

also add missing ".El", s/Toggles/Toggle/ in second command and add newlines
after a full stop

document mouse button actions

[sevz: commit message is mine. The content was written by scottro11 and shared
in https://codeberg.org/dwl/dwl/issues/697]

Closes: https://codeberg.org/dwl/dwl/issues/697

drop CAVEATS section from the man page

Since 71f11e6cf63289d51f152469a0da81a85fe2608c it is not longer the case

Use `all-scroll` instead of `fleur` xcursor shape for window dragging

When there are no xcursor themes available, Wayland uses its own built-in shapes [1].
Wayland (and thus to extend wlroots) is based on the XDG's cursor spec [2],
which itself is based on CSS' [3][4], neither of which define `fleur` shape. So dwl,
without any external themes, falls back to `default` shape when dragging a window.
There is `all-scroll` shape that is being symlinked to (or vice versa) by `move`,
`dnd-move`, `grabbed` and `fleur` shapes by various themes.

Since `all-scroll` is being symlinked to anyway, and has been part of all relevant
specs as the shape for this use case for a very long time now, use it instead.

[1] https://gitlab.freedesktop.org/wayland/wayland/-/blob/main/cursor/cursor-data.h#L559
[2] https://www.freedesktop.org/wiki/Specifications/cursor-spec
[3] https://drafts.csswg.org/css-ui/#cursor
[4] https://developer.mozilla.org/en-US/docs/Web/CSS/cursor

Fix crash disabling monitor with locked surface

Revert "Update config.mk"

This reverts commit 7d2415bfe854cccc2bcf2709fecc1eaacddbe903.

Will stick with wlroots 0.19 for now.

Update config.mk

compiles and works fine on wlroots-0.20

Cleanup comments

Update README.md

fix: shouldn't configure uninitialized layer_surface

fix: crash when open some x11 app

allocate with LISTEN_STATIC

Fixes: https://codeberg.org/dwl/dwl/issues/723
Supersedes: https://codeberg.org/dwl/dwl/pulls/724

rename some listeners

To keep consistency with the rest of listeners

destroy keyboard group after unlinking listeners

Last commit addressing the issue mentioned in
0925fe956aeddb983875f0fd892e9049e2d8cb76

unlink global listeners on destroy

Continuation of 0925fe956aeddb983875f0fd892e9049e2d8cb76

Partially revert "Line saver: LISTEN_STATIC macro"

This reverts commit 33bcd2e4ca892bb0b558660c99ed63a3dfdd9011.

We keep LISTEN_STATIC for three instances where we use it. We use
simple listeners for the rest of signals.

This is the continuation of 0925fe956aeddb983875f0fd892e9049e2d8cb76