README.md: Fix grammatical error, adjust wording
README.md: Fix grammatical error, adjust wording

libqtxdg/libqtxdg,luis-pereira/libqtxdg,lxde/libqtxdg,lxde/libqtxdg,libqtxdg/libqtxdg,luis-pereira/libqtxdg