Add support for Rails 7

[tachyons]

Issue #164 , if available:

Summary

Relax rails version dependency to support rails 7

Other Information

[simukappu]

Thank you for creating this PR. We'd like to allow use with Rails 7.0, but the gem is not tested with Rails 7.
Can you add test gemfile to gemfiles directory and confirm if it works fine?

[simukappu]

We've allowed use with Rails 7.0 in #164. Closing this PR.