v3.0.0

https://github.com/slackapi/python-slack-events-api/milestone/3?closed=1

• Updates for Flask 2.x compatibility - thanks @antonio-te @seratch

Migration guide:

Since this version, this package no longer works with:

• Python 2.7
• Flask 1.x

Please use Python 3.6 or higher along with Flask 2.x.