Well, you probably already know that C++ isn’t a great language to code a Discord bot, since you could use Python or Node.js and get one up and running in a few minutes. That being said, you can find libraries on GitHub for Discord API written for C++. Here are two GitHub repositories that provide C++ libraries and instructions on how to download them for coding a Discord bot in C++: repo 1 and repo 2.
According to Discord, There are 3 libaries for Discord API. They are:
Aegis.cpp
D++
Sleepy Discord
You can click this for more resources (some might not included).