TejaHarjaKusumah just-do-it
You can install an extension named Emoji Picker which shows all available emojies and allows to insert them with a mouse click.
The second way to insert an emoji is to just type a colon and then guessing (or remembering) its name. If you e.g. type :griyou will have a popup offering (beneath others):grin: ?, :grinning: ? and :grimacing: ?.