Add merveilles.town to mastodon instance whitelist

[aadilayub]

I was trying to link my mastodon profile to my dev.to account, but got an error saying it wasn't in the list of approved instances. The instance I use is merveilles.town, a group of creative technologists.

For reference, here are the instances' rules and values.

[rhymes]

Thanks @aadilayub, sent a PR about it: #7983 :-)

[aadilayub]

Thanks @rhymes!

[dar5hak]

Hello. I'm here to request another instance to be allowed: https://im-in.space/. It's a small, general-purpose instance with ethical rules in place. Can we reopen this?

I was having an email conversation with Michael who directed me here. Thanks.

[rhymes]

@dar5hak would you like to open a PR about this? It's simple as adding the hostname to https://github.com/forem/forem/blob/master/app/lib/constants/mastodon.rb

[dar5hak]

@rhymes Thanks for guiding. Here we go.