system: add catatonit as init system
Like the existing tini, catatonit can be used as minimal init to be
used as PID-1.
Add it to the list of init systems, like was done for tini in
24cac9c4e6a3 (system: add tini as init system) and tinyinit in
c1daa35cd950 (package/tinyinit: new package).
Unlike the "main" init systems, there is no historical preference for
those minimalist init systems, so just keep them alphabetically
ordered.
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Julien Olivain <ju.o@free.fr>