Copy gemfile from xray

Author: ollym

propagator/google_cloud_trace_context/Gemfile

@@ -5,7 +5,15 @@ source 'https://rubygems.org'
 gemspec
 
 group :test do
+  gem 'bundler', '~> 2.4'
+  gem 'minitest', '~> 5.0'
+  gem 'rake', '~> 13.0'
+  gem 'rubocop', '~> 1.75.1'
+  gem 'rubocop-performance', '~> 1.24.0'
+  gem 'simplecov', '~> 0.22.0'
+  gem 'yard', '~> 0.9'
   if RUBY_VERSION >= '3.4'
+    gem 'base64'
     gem 'mutex_m'
   end
-end
+end