"pacman" should be listed instead of "arch" under "Other candidate types to define"

[bronze51]

The Arch distro uses the pacman package manager. Other pacman based distros are listed here: https://en.wikipedia.org/wiki/Category:Pacman-based_Linux_distributions I recommend that "arch" in the "Other candidate types to define" list is replaced with "pacman"

[Foxboron]

Please see https://github.com/package-url/purl-spec/pull/164