Check for known emote names and replace them with an embedded image of the emote.
Also supports modifiers similar to BetterDiscord's emotes.

Install BetterDiscord from here
https://github.com/BetterDiscord/Installer/releases
Reminder: BetterDiscord is against the TOS, use at your own risk!

Download this library https://raw.githubusercontent.com/rauenzi/BDPluginLibrary/master/release/0PluginLibrary.plugin.js
And the plugin: https://raw.githubusercontent.com/Yentis/betterdiscord-emotereplacer/master/EmoteReplacer.plugin.js
(Rightclick -> Save as...)

Open Discord -> Settings -> Plugins -> Open plugin folder and place the 2 plugins there.
Enable them in the Plugins menu and hit Ctrl + R.

Custom emotes can be added and prefix can be changed through the settings menu.
Begin typing emote names as you would regular Discord emotes with ; instead of :

You can also use any existing Discord emotes along with whatever modifiers you like.
Just type them as usual and they will be sent as an image if you don't currently have nitro.

Gif utils code: https://github.com/Yentis/emotereplacer-gifutils
List of emotes: https://yentis.github.io/emotes

Modifiers can be chained!
.flip - Flip emote horizontally.
.flap - Flip emote vertically.
.rotate-<degrees> - Rotate emote by x degrees.
.speed-<speed> - For gifs, change delay between frames in hundredths of a second.
.hyperspeed - Remove every other frame and set delay to the minimum for extreme speed.
.reverse - Make a gif play backwards.
.spin-<speed> - Make your emote spin! Speed can be: left empty, fast, faster or hyper.
.spinrev-<speed> - Same as above but spin in the other direction.
.slide-<speed> - Make your emote slide! Speed can be: left empty, fast, faster or hyper.
.sliderev-<speed> - Same as above but slide in the other direction.
.shake-<speed> - Make your emote shake! Speed can be: left empty, fast, faster or hyper.
.rainbow-<speed> - Make your emote strobe with a rainbow of colors! Speed can be: left empty, fast, faster or hyper.
.infinite-<speed> - Make your emote pulse outwards! Speed can be: left empty, fast, faster or hyper.
.wiggle-<intensity> - Make your emote wiggle! Intensity can be: left empty, big, bigger or huge.
.wide-<wideness> - Make your emote extra wide! Wideness can be: left empty, big, huge, extreme or a number from 2 to 8.
.resize-<size> - Resize your emote. Can be: small, medium, large or a number from 32 to 128.
.rain-<option> - Add a rain effect to the emote. Option can be: left empty, glitter.

Examples:
;yentDogSmug.flip
;yentKrisDance.speed-5
;yentKannaDance.rotate-90

Size - Emotes can be 32 to 128px large, with 48 being the normal emote size.
Spoilers - Emotes can be hidden behind a spoiler using spoiler tags.