readme: Add discuss section
proto: use uint32_t offsets and message lengths

As the protocol imposes a hard 32-bit limit on message size, and the
affected functions' offset value can never go negative, just use
uint32_t for the lot. Fully fixes the signedness errors partially
corrected in b8218e3fae78fc9977fa867a121ae11b2ab35d4e while avoiding
the possibility of silent truncation (either through an overlong
message or running on a big-endian host).
man: Elaborate on stylesheets a bit
meson: Update version properly
proto: Fix signed-ness error
ci: Disable automatic github mirroring
Convert -Dlayershell to 'feature'
man changes for --style option
Add support for user CSS styles.

Add a few element names to simplify styling.

Example with transparent bg and swaybg (for Adwaita-dark theme):
window { background-color: transparent; }
box#body {
    background-color: #353535;
    box-shadow: 1 0 0 1px rgba(27, 27, 27, 0.9);
    padding: 50px;

Example with background-image:
window {
  background-image: url("file:///usr/share/backgrounds/default.png");
  background-size: cover;
  background-position: center;
box#body {
    background-color: #353535;
    box-shadow: 1 0 0 1px rgba(27, 27, 27, 0.9);
    padding: 50px;
Use layer-shell anchors to fill the screen

The change fixes interactions with other layer-shell windows and allows
to react to output size changes automatically.
Fix --command argument for builds without layer-shell
Remove gtk-application-prefer-dark-theme

This was a hack introduced while debugging broken Gtk theme selection.
It does nothing when theme selection is broken, and when it works, the
user can just pick a theme (including dark variants) with e.g. gsettings.
man: Document the background image flag
Add support for background images
Remove action_quit
Fix dropdown resetting under layer-shell

window_setup unconditionally recreated the entire input section every
time it was called. As window focus results in window_setup being called
when layer-shell is active, this mean that the focus change caused by
interacting with the dropdown would result in the dropdown being
destroyed and recreated, resulting in it being reset to the initial

Only recreate the input section if question has changed to avoid resets,
and copy the active dropdown selection index if output focus changes to
improve usability.

Live edits to the dropdown entry are still lost on output change.
strdup question to avoid use-after-free/return
Only resize clock when necessary
Ensure that clock resizes correctly
Fix linkage on Fedora 32