[Feature Request] Add welcome email

[phoenixpereira]

Overview

Create a welcome email and automatically send it when a user pays for membership.

Details

• Create a welcome email using react email and tailwind.
• Use nodemailer to send the email.
• Automatically send the email when a user pays for membership (either by themselves or when a committee member marks them as paid).
• Requires an extra db field to check whether the welcome email has been sent or not

Why would this feature be useful?

So that club members can get a welcome email with useful info and links.

Additional Notes

Part of #31

[phoenixpereira]

Merged in #232.