Add irb to Gemfile

```shell
$ irb
3.4.0/gems/irb-1.14.3/exe/irb:7: warning: irb was loaded from the standard library, but will no longer be part of the default gems starting from Ruby 3.5.0.
You can add irb to your Gemfile or gemspec to silence this warning.
3.4.0/irb/input-method.rb:278: warning: rdoc was loaded from the standard library, but will no longer be part of the default gems starting from Ruby 3.5.0.
You can add rdoc to your Gemfile or gemspec to silence this warning.
```

Author: viralpraxis

Gemfile

@@ -7,6 +7,7 @@ git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 gemspec
 
 gem 'bump', require: false
+gem 'irb'
 gem 'rake'
 gem 'rspec'
 gem 'rubocop', github: 'rubocop/rubocop'