Implement Application Command cooldowns

[spifory]

Summary

Command cooldowns should be implemented into Application Commands.

What is the feature request for?

Application commands

The Problem

Adding command cooldowns to Application Commands would be great, as the user's bot would notify their user that they are using the command too frequently.

The Ideal Solution

Adding command cooldowns to Application Commands, they should somewhat work the same way that ext.commands's cooldown system works.

The Current Solution

The current solution for users would be to use https://github.com/Skelmis/Function-Cooldowns (which is what people have likely been using for a while now).

Additional Context

This was initially discussed in the nextcord guild, however it has not been worked on by the person who planned to do it, hence why this issue is made so late.