Could not find gem github-pages in locally installed gems

Hi, thanks for reading.
I am getting a “C:/Ruby31-x64/lib/ruby/gems/3.1.0/gems/bundler-2.3.26/lib/bundler/resolver.rb:235:in `block in verify_gemfile_dependencies_are_found!': Could not find gem ‘github-pages (= 227)’ in locally installed gems. (Bundler::GemNotFound),” error when I uncomment

gem "github-pages", "227", group: :jekyll_plugins

and comment out # gem "jekyll", "~> 3.9.2"

I have following instructions from the github help page as earlier support material didn’t suggest to add the github-pages version.

The jekyll website works fine on my github pages when I have uncommented gem “jekyll” line. But I am trying to add the minimal-mistakes-jekyll theme to my jekyll site and I suppose I need to comment the jekyll version line to add the theme line. But I am just a novice so any direction would be appreciated.

Below is my gemfile

source ""
# Hello! This is where you manage which Jekyll version is used to run.
# When you want to use a different version, change it below, save the
# file and run `bundle install`. Run Jekyll with `bundle exec`, like so:
#     bundle exec jekyll serve
# git_source(:github) {|pravin-vaz| "{pravin-vaz}" }
# This will help ensure the proper Jekyll version is running.
# Happy Jekylling!
# gem "jekyll", "~> 3.9.2"
# This is the default theme for new Jekyll sites. You may change this to anything you like.
gem "minimal-mistakes-jekyll"
gem "github-pages", "227", group: :jekyll_plugins
# previous version was "minima", "~> 2.5" 
# If you want to use GitHub Pages, remove the "gem "jekyll"" above and
# uncomment the line below. To upgrade, run `bundle update github-pages`.

gem "jekyll-include-cache", group: :jekyll_plugins

# If you have any plugins, put them here!
group :jekyll_plugins do
  gem "jekyll-feed", "~> 0.12"

# Windows and JRuby does not include zoneinfo files, so bundle the tzinfo-data gem
# and associated library.
platforms :mingw, :x64_mingw, :mswin, :jruby do
  gem "tzinfo", ">= 1", "< 3"
  gem "tzinfo-data"

# Performance-booster for watching directories on Windows
gem "wdm", "~> 0.1.1", :platforms => [:mingw, :x64_mingw, :mswin]

# Lock `http_parser.rb` gem to `v0.6.x` on JRuby builds since newer versions of the gem
# do not have a Java counterpart.
gem "http_parser.rb", "~> 0.6.0", :platforms => [:jruby]