Use bundle add in README installation instructions (#1287)

Use `bundle add` in README installation instructions, to reduce the steps needed to start using the gem.

Co-authored-by: David Rodríguez <deivid.rodriguez@riseup.net>

README.md

@@ -17,17 +17,16 @@ or controller layer, you're probably not looking for Ransack.
 
 Ransack is supported for Rails 7.0, 6.x on Ruby 2.6.6 and later.
 
-In your Gemfile, for the last officially released gem:
+To install `ransack` and add it to your Gemfile, run
 
 ```ruby
-gem 'ransack'
+bundle add ransack
 ```
 
-If you would like to use the latest updates (recommended), use the `master`
-branch:
+If you would like to use the latest updates, use the `master` branch:
 
 ```ruby
-gem 'ransack', github: 'activerecord-hackery/ransack'
+bundle add ransack --github "activerecord-hackery/ransack"
 ```
 
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