Reintroduce XDG_VTNR

Some X11 start scripts rely on this variable to apss the current VT to
Bump version to 0.10
Update dependencies
readme: Add Phog greeter implementation

Signed-off-by: fossdd <fossdd@pwned.life>
Update dependencies
man: Document VT switch
config: Drop support for old config format

The support for the old config format was meant to ease transition and
has now served its purpose.
Allow overriding VT via arguments
Deduplicate parsing of VtSelection
agreety: Update nix to 0.27
pam: Swap /etc/pam.d and /usr/lib/pam.d
pam: Remove fallback to the login service

This is just an old legacy feature, no need to carry it around anymore.
Users need to ensure that there is a service file for greetd, and if
they are free to copy the one intended for login(1).
pam: Check /usr/lib/pam.d

We do some presence checks before using certain PAM service files. Check
/usr/lib/pam.d in addition to /etc/pam.d.
Update dependencies
readme: Add two greeter implementations
chore: set dir to absolute path
Derive VtSelection::default
Use strip_prefix to strip prefix

No need to do it manually.
Remove pointless copying of string before copying it
Remove references that are implicitly dereferenced

This are implicitly dereferenced by the compiler and a no-op.