graphics/eom: switch to GitHub release asset, convert to Meson

1.28.1 is no longer published to the MATE mirror and is only available
on GitHub. The build system switched from autotools to Meson in this
release. Remove autoreconf, yelp-tools, gtk-doc, and autoconf-archive
build deps, no longer needed. Remove gnomeprefix from USE_GNOME as it
sets CONFIGURE_ARGS which is incompatible with Meson. Update OPTIONS
to use MESON_ENABLE. Update pkg-plist: add scalable action SVG icons
and thumbnailer, remove three help locales not installed by Meson.