Resolve "As a Streamer I would like to deploy the app on Heroku"

Makes it possible to have Heroku support Closes #3 (closed)

Changelog

Fixed:

• Allows multiple Browser Source using "pipes" for channels

Added:

• Heroku button in README
• PORT env variable support for Heroku

Checklist

Ensure that before making this PR you have:

• Read the contributing guidelines
• Agreed with the LICENSE
• Run go fmt ./...
• Run go mod tidy