Match constant definition with the file name

Although parser_selection is why those methods exists, they all exist
in Rails::Dom::Testing module. Following Rails convetions, it is better
to define the name of the file matching the name of the constant.

lib/rails-dom-testing.rb

@@ -1,5 +1,4 @@
 # frozen_string_literal: true
 
-
+require "rails/dom/testing"
 require "rails/dom/testing/railtie" if defined?(Rails::Railtie)
-require "rails/dom/testing/assertions"

lib/rails/dom/testing/parser_selection.rb → lib/rails/dom/testing.rb

@@ -1,7 +1,12 @@
 # frozen_string_literal: true
 
+
+require "nokogiri"
+require "active_support"
 require "active_support/core_ext/module/attribute_accessors"
 
+require "rails/dom/testing/assertions"
+
 module Rails
   module Dom
     module Testing

lib/rails/dom/testing/assertions.rb

@@ -1,8 +1,5 @@
 # frozen_string_literal: true
 
-require "nokogiri"
-require "active_support"
-
 require_relative "assertions/dom_assertions"
 require_relative "assertions/selector_assertions"
 

lib/rails/dom/testing/assertions/dom_assertions.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "../parser_selection"
-
 module Rails
   module Dom
     module Testing

lib/rails/dom/testing/assertions/selector_assertions.rb

@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "../parser_selection"
 require_relative "selector_assertions/html_selector"
 
 module Rails

lib/rails/dom/testing/assertions/selector_assertions/html_selector.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "minitest"
-require "active_support/core_ext/module/attribute_accessors"
 
 require_relative "substitution_context"