Update Gemfile to use custom gemfile process for manual dependency injection

Author: jsklan

.fernignore

@@ -1,9 +1,9 @@
 lib/square_legacy/
 lib/square_legacy.rb
-Gemfile
 Rakefile
 .gitignore
 test/
 .github/workflows
 README.md
 lib/square/file_param.rb
+custom.gemfile.rb

.gitignore

@@ -1,3 +1,5 @@
 pkg
 *.gem
 CLAUDE.md
+vendor/
+.bundle/

Gemfile

@@ -7,16 +7,17 @@ gemspec
 group :test, :development do
   gem "rake", "~> 13.0"
 
-  gem 'minitest', '~> 5.20'
+  gem "minitest", "~> 5.16"
   gem "minitest-rg"
 
-  gem 'mutex_m'
-  gem 'base64'
-
   gem "rubocop", "~> 1.21"
   gem "rubocop-minitest"
 
   gem "pry"
 
   gem "webmock"
 end
+
+# Load custom Gemfile configuration if it exists
+custom_gemfile = File.join(__dir__, "custom.gemfile.rb")
+eval_gemfile(custom_gemfile) if File.exist?(custom_gemfile)

Gemfile.lock

@@ -144,7 +144,7 @@ PLATFORMS
 
 DEPENDENCIES
   base64
-  minitest (~> 5.20)
+  minitest (~> 5.20, ~> 5.16)
   minitest-proveit (~> 1.0)
   minitest-rg
   mutex_m

custom.gemfile.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+# Custom Gemfile configuration file
+# This file is automatically loaded by the main Gemfile. You can add custom gems,
+# groups, or other Gemfile configurations here. If you do make changes to this file,
+# you will need to add it to the .fernignore file to prevent your changes from being
+# overwritten by the generator.
+
+# Example usage:
+# gem 'custom-gem', '~> 1.0'
+# 
+# group :development do
+#   gem 'debug-gem', '~> 2.0'
+# end
+
+# Add your custom gem dependencies here
+
+group :test, :development do
+  gem 'mutex_m'
+  gem 'base64'
+end