Suggested-by: yamlllint

Suggested-by: cppcheck

Since the parameters are unused, just prefix them with an underscore.

Suggested-by: cppcheck

They don't create files so aren't real targets.

Some BSD install programs don't have the -D option to create the dir.

The file is already deleted and deletion was desired,
so don't fail when the desired state was already present.

This will be helpful for distributions packaging the plugin.

Use a symlink instead of installing a binary in the /etc directory,
since that is meant to be configuration files only, unfortunately
mpv does not load plugins from anywhere in the /usr directory tree.

Support the DESTDIR variable for overriding the rootfs location
and support overriding the PREFIX and the plugin directories.

This also works when using fakeroot and that will help distributions
automatically install to the mpv system wide scripts directory.

The plugin should work on GNOME/KDE on the BSD disributions too,
and the abbreviation "DEs" is not fully obvious at first glance.

Separate out the different parts of the process to use the plugin.

Everyone will need to know what their system mpv needs before they can
figure out if they will be able to use the plugin on their system,
so put the information about that first.

Most people (except some distro users) will need to know where mpv loads
the plugin from, so put that before the install instructions.

The install instructions are only needed once by most people,
so move them down but before the build instructions.

Mention the pre-built 64-bit Linux binary is for x86, since
the 64-bit ARM architecture is becoming popular with Apple M1 etc.

Add mention of the distro packages (via repology.org) as an install option
and put it first, it is an option that many open source users prefer.

The build instructions are needed by the fewest people so they go next,
since there are distro packages and a pre-built 64-bit x86 Linux binary
that people can try before they need to resort to building from source.

Leave the D-Bus interfaces at the very end since most people except devs
won't need to know the details and it is more technical documentation.