MXKEventFormatter: Add singleEmojiTextFont property to special case the display of message with a single emoji.
MXKEventFormatter: Add singleEmojiTextFont property to special case the display of message with a single emoji.

https://github.com/vector-im/riot-ios/issues/1157: optionally boost size of lone emoji like on riot-web

vector-im/vector-ios,vector-im/vector-ios,vector-im/riot-ios,vector-im/vector-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios