Change Arch Linux install instructions

[payl0ad]

(Small and not important)

install instructions on arch linux are as follows:

yaourt -S wallpaperdownloader

Yaourt is outdated, unmaintained, not secure. Source: https://wiki.archlinux.org/index.php/AUR_helpers Also not everyone has yaourt on arch, anyway perhaps the author should change install instructions for arch linux Alternatives:

trizen -S wallpaperdownloader

or

 yay -S wallpaperdownloader 

[Eloy García Almadén]

The Wiki has been changed accordingly.

Thank you very much @AllTheseGitChoisesNGithubAint1 for your contribution in the improvement of the Wiki and the documentation!!! :)

If you see something more, please don't hesitate to contact me or open a new issue!!