Replies don't copy mentions

When you reply to a post, it should automatically fill the reply form with the people already tagged in the conversation

For example, if we have a status by @account0 that reads something like @account1 very cool, it will have a mentions property with an array of objects like [{ acct: 'account1@myinstance.com', ... }, { acct: 'account0@anotherinstance.com' }]

When you reply to that status, it should already fill the reply field with @account0@anotherinstance.com @account1@myinstance.com, but also making sure to remove your own account from the list if it's included.

Basically we want the behavior to be the same as on pleroma-fe in this regard.