required_ruby_version in gemspec

[innawy]

Hi! I came across the below offense during the build process of script/cibuild. I'm not sure how to fix this.

Offenses:

jekyll-theme-minimal.gemspec:1:1: C: Gemspec/RequiredRubyVersion: required_ruby_version should be specified.
# frozen_string_literal: true
^

3 files inspected, 1 offense detected
Error: Process completed with exit code 1.

I have tried adding the line below in jekyll-theme-minimal.gemspec, however which required ruby version should I be using?
s.required_ruby_version = '2.4.0'

Thank you!

[parkr]

Hello! I have resolved this on the master branch. Thanks!