add default snapper config for apk-snap

See merge request !3

add: snapper-config tailored to apk-snap

See merge request !2

apk_snap.py: replace pre/post commit argument logic with .removesuffix(), ensure consistent variable names

Replace hook script with symlink

See merge request !1

re-add '/' to install destination, as pkg introspection revealed the executable was being installed to /usrbin/ and not /usr/bin/

move install of hook to bottom of install section, in hopes of avoiding the hook calling for apk-snap before the executable's been fully installed

change Makefile: make sure all install lines use the  variable, to avoid breaking the fakeroot build env

change Makefile: install apk-snap to /usr/bin/, rather than /bin. Add $DESTDIR variable as /, before all hardcoded install destinations."