Split out documentation into separate package to reduce size.

Signed-off-by: David Runge <dvzrv@archlinux.org>

Signed-off-by: David Runge <dvzrv@archlinux.org>

archlinux/devtools!109 (comment 74475)

Temporary workaround for a test failure in libzim, to unblock icu 71.

Add call to autoreconf in prepare().
Add all direct (library) dependencies in depends. Add all sodeps in package() and respective package in makedepends().
Add call to make check in check(). Change to correct license (GPL2).
Add libxapian.so to provides. Add additional docs. Add contributor info.