Prepare changelog for v0.4.7

Create detector surface in layer overlay

Up to sway 1.9, wl_surface::enter events were delivered to layer shell
surfaces even if they were not visible. With the latest (yet unreleased)
changes, this is no longer the case.

Strictly speaking, a compositor may delay the wl_surface::enter event
until the surface is visible, so ensure that it is always made visible.

See: https://github.com/swaywm/sway/issues/7984

Fix build in Rust 1.8.0

Rust itself had some backwards incompatible changes. Older versions of
`time` no longer build.

Fixes: https://todo.sr.ht/~whynothugo/shotman/33

Remove pointless clone

Move DesiredTarget out of main state

Minor readme improvements

readme: remove missing features

See: https://todo.sr.ht/~whynothugo/shotman/29
See: https://todo.sr.ht/~whynothugo/shotman/30

Prepare changelog for v0.4.6

Split changelog into a separate file

readme: tidy up sway instructions

Update copyright year

Improve ambiguous error names

Remove _state suffix from State properties

Improve logging for released buffers

Add missing backtick

Adapt to recent changes in wl_buffer protocol

Destroying buffers now implicitly detaches them, so the lifetime of each
buffer needs to be manually tracked.

See: https://gitlab.freedesktop.org/wayland/wayland/-/merge_requests/363

This has been fixed in wayland-rs

Explicitly match ()

Use empty type to identify Dispatch impls

Update copyright email