Add irb to railties' dependencies

- Firstly, including irb as a dependency allows users with older versions
  of Ruby to benefit from the latest version of irb, instead of being
  limited to the version bundled with their Ruby installation.

- Additionally, there is an [ongoing discussion](https://bugs.ruby-lang.org/issues/19351) to move irb to bundled gems.
  If this change is implemented, users may need to declare irb in their
  Gemfile in order to use it for Rails console. By adding irb as a dependency,
  users can avoid the extra effort of manually specifying irb in their Gemfile.

Gemfile.lock

@@ -96,6 +96,7 @@ PATH
     railties (7.1.0.alpha)
       actionpack (= 7.1.0.alpha)
       activesupport (= 7.1.0.alpha)
+      irb
       rackup (>= 1.0.0)
       rake (>= 12.2)
       thor (~> 1.0)

railties/CHANGELOG.md

@@ -23,6 +23,13 @@
 
     *Xavier Noria*
 
+*   Railties now requires the irb gem as a dependency, which means when you install Rails, irb will also
+    be installed as a gem. Rails will then use the installed version of irb for its console instead of
+    relying on Ruby's built-in version.
+    This ensures that Rails has access to the most up-to-date and reliable version of irb for its console.
+
+    *Stan Lo*
+
 *   Use infinitive form for all rails command descriptions verbs.
 
     *Petrik de Heus*

railties/railties.gemspec

@@ -44,6 +44,7 @@ Gem::Specification.new do |s|
   s.add_dependency "rake", ">= 12.2"
   s.add_dependency "thor", "~> 1.0"
   s.add_dependency "zeitwerk", "~> 2.6"
+  s.add_dependency "irb"
 
   s.add_development_dependency "actionview", version
 end