Reopened from slackapi/node-slack-interactive-messages#46

Description

1. The SLACK_ACCESS_TOKEN variable is only available after install, but if you try to install the app in the order the instructions are presented, it will fail and say you need to add at least one scope.

2. In enabling interactive components, where do I get the "Glitch URL"? Its in the "Share" menu, but it would be nice to be explicit. Maybe give an example.

3. Where do I put the environment variables? If you know Glitch, you'll know its in 🗝.env, but many users don't know Glitch. Also, if you're running locally, its not clear that you can put this in .env.

4. You need a description for the slash command.

5. PORT needs to be commented out in .env

6. In package.json, @slack/interactive-messages dependency version specifier should be set to "^0.3.0"

Maybe there should be 2 completely different sets of instructions for setup locally and on Glitch.

What type of issue is this? (place an x in one of the [ ])

• bug
• enhancement (feature request)
• question
• documentation related
• testing related
• discussion

Requirements (place an x in each of the [ ])

• I've read and understood the Contributing guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've searched for any related issues and avoided creating a duplicate issue.