BondrewdLikesHisEmotes is a powerful, easy to use and versatile plugin that makes anything to do with unicodes a seamless process.
The core of it was aimed at making emojis/emotes usable in chat, much like Discord.

Been using it for our project for a few years now and decided to post it up here aswell. Over time it got several features and has become essentially an all encompassing plugin for anything related to unicodes and fonts.

It lets you easily add new emojis and GIFs but is also useful for creating custom menus, hud elements and so on. Simply adding the placeholder to just about anywhere will display the intended unicode.

Works for signs, books, chat, inventory titles, tablist, scoreboards.
It also works with DiscordSRV to translate emotes between Minecraft and a Discord Chat. In essence, if you wanna use a custom unicode somewhere, this will make the process painless.

For more info take a look at the README
For more config examples you can check out our repo here
The plugin does not come with any default emojis/GIFs/textures, and you have to get them all yourself.

Some premium packs you could buy:
https://mcmodels.net/model/emojis-pack-v1/
https://mcmodels.net/model/meme-emojis-pack/