Option to disable browsing public groups

[geckolinux]

Your use case

Hi there, would it be possible to add an option, (preferably with an optional password for disabling it) to disable browsing public Matrix groups on the homeserver? I would like to move most of my contacts to Matrix, but some of them need a light parental control option and/or the option of disable NSFW stuff from appearing, so some of the public groups that exist on most homeservers are a problem in that regard. Of course somebody could still find ways to get into those groups if they wanted to, but it a simple hide button for public groups would be enough for most of the users I'm trying to switch, and it should be easy to implement. I floated this idea in #282 and it was suggested that the option should be disabled on the homeserver; however I strongly disagree, because a "normal" user will always be using a large public Matrix server and those will always have public groups enabled. Simply disabling the option of browsing groups on the client side seems to be the easiest way of reducing this barrier to entry for potential Matrix users. Thanks for considering this!

Have you considered any alternatives?

I've tried all the other cross-platform Matrix clients, and they all allow for browsing public groups on the homeserver.

Additional context

Related:
#282