Add "listed/unlisted" visibility to charmhub.io

[taurus-forever]

Hi,

The charm has two independent options for:

• visibility (public/private)
• search-ability (listed/unlisted)

Unfortunately the last settings are invisible on WEB interface which created confusion (example).

It is a new feature request ticket to add column "Listing" to https://charmhub.io/charms
It should significantly help charm maintainers to be sure, the charm is fully "published" => increase QoS.

Example:

Thank you!
P.S. ability to set public/private/listed/unlisted on WEB interface is another great feature! ;-)