[Feature] Add @ as option to auto suggest nicknames if Suggest nicknames as you type is turned off

[TehPeGaSuS]

Currently we need to have Suggest nicknames as you type enabled to have nicks auto suggested while typing.

Although the feature is nice, it's a bit annoying to have half of the screen pledged with suggestions just because 100 nicks match the first two letters of the word we are writing and seems to make the app to lag a little bit.

Personally, I've disabled auto suggestion and double tap a message to mention a user.

It would be nice to have an option to disable auto suggestion but to be able to mention a nickname prefixing the word with a @ instead.

I know that this might conflict with the way IRCCloud deals with Slack mentions, but it would be probably possible to make the app distinguish between normal IRC connections and Slack and auto remove the @ prefix in a normal connection?

Cheers