Include detailed instructions of Privileged Gateway Intents for Discord Integration in README.md

[xayanide]

Description
https://discordjs.guide/preparations/setting-up-a-bot-application.html#token-leak-scenario

That link alone doesn't give users instructions about enabling the required privileged intents that osu-ahr uses and needs.
The link's enough for setting up a simple bot, but there are no instructions for enabling of privileged intents.

Include detailed instructions in Discord Integration section in README.md to prevent users from encountering Priveleged Intents kind of issues.

Probably can add those instructions here https://github.com/Meowhal/osu-ahr#creating-your-bot