Support Reminders

[Fausto95]

We have weekly events, it'd nice if we could set a reminder so the bot would send them periodically in the #general channel.

We could use a prefix like !reminder and pass the arguments right after.
The args would be something like:

• Date: The date that the reminder is scheduled to be sent.
• Repeat: A boolean.
• Interval: The interval(in minutes) that the reminder should be sent.
• Message: The message(in between quotes) we should send to the users.

So the message would look like: !reminder 2020-05-29 true 30 "Hello world".

Likely we'd tag users within the message. It'd be nice to instead put placeholders, and provide a comma separated list of username's.
So we'd support a 5th argument:

• users: A comma separated of usernames or ids.

So the message would now look like: !reminder 2020-05-29 true 30 "Hello world $user, do you now $user?" @john,@mauro.

Guide: https://discordjs.guide/
Docs: https://discord.js.org/#/docs/main/stable/general/welcome