Update Arch Linux package links

Arc theme has made it to the official Arch Community package repo meaning Arch users can now install the official releases directly from pacman! The development releases will still be available from the AUR.

README.md

@@ -62,11 +62,11 @@ http://software.opensuse.org/download.html?project=home%3AHorst3180&package=arc-
 
 --
 
-Arch Linux users can install the theme from the AUR
+Arch Linux users can install the official releases directly from pacman in the Community repo and development releases in the AUR 
 
-**Official Releases**: https://aur.archlinux.org/packages/gtk-theme-arc/  
+**Official Releases**: [arc-gtk-theme](https://www.archlinux.org/packages/community/any/arc-gtk-theme/)
 
-**Development Releases**: https://aur.archlinux.org/packages/gtk-theme-arc-git/  
+**Development Releases (AUR)**: [gtk-theme-arc-git](https://aur.archlinux.org/packages/gtk-theme-arc-git/)
 
 **Note:** If you're having trouble with the AUR packages please email the package maintainer at [email protected] before creating an issue.