don't capitalize "berg" in "Codeberg" spelling. Codeberg's official
sites does not seem to do so.
switch from "GPLv2" to "GPL-2.0-or-later" according to the spdx short
identifier: https://spdx.org/licenses/GPL-2.0-or-later.html
explicitly mention that Imlib2 needs to be built with X11 support.
Reviewed-on: https://codeberg.org/nsxiv/nsxiv/pulls/470
Reviewed-by: explosion-mental <explosion-mental@noreply.codeberg.org>
d19924f288