Remove deprecated require shims and fix require_relative issue

Remove lib/xml.rb and lib/xml/libxml.rb which were deprecated entry
points that polluted the global namespace. Use require 'libxml-ruby'
instead.

Revert require_relative back to require for loading the C extension
so RubyGems can find the .so via $LOAD_PATH when installed as a gem.

Update docs and changelog.

Fixes #226

Author: cfis

CHANGELOG.md

@@ -15,7 +15,7 @@ Breaking changes:
 * Remove deprecated Document methods: dump, format_dump, debug_dump, debug_dump_head, debug_format_dump, reader
 * Remove deprecated Parser.register_error_handler (use Error.set_handler)
 * Remove deprecated HTMLParser#file=, #io=, #string= (use class methods HTMLParser.file, .io, .string)
-* Remove deprecated require paths: require 'libxml' and require 'xml/libxml' (use require 'libxml-ruby')
+* Remove deprecated require paths: require 'libxml', require 'xml/libxml', and require 'xml' (use require 'libxml-ruby')
 * Fix misspelled Schema::Type#annonymus_subtypes -> anonymous_subtypes
 
 The release also includes a number of smaller improvements, including:
@@ -32,6 +32,10 @@ The release also includes a number of smaller improvements, including:
 * Remove dead Float::INFINITY definition for Ruby 1.8.7
 * Add mswin CI job using vcpkg for libxml2
 * Minimum Ruby version is now 3.2
+* Revert require_relative back to require for loading the C extension (fixes #226)
+* Allow nil for external and system IDs when creating a DTD (fixes #215)
+* Fix C14N document subset canonicalization with namespace nodes
+* Enable W3C C14N spec tests 3.5 (entity references) and 3.7 (document subsets)
 * Rename HISTORY to CHANGELOG.md, README.rdoc to README.md
 
 == 5.0.6 / 2026-04-03

docs/getting_started.md

@@ -2,22 +2,14 @@
 
 ## Requiring the Library
 
-There are several ways to load libxml-ruby:
-
 ```ruby
-# Recommended - keeps everything under the LibXML namespace
 require 'libxml-ruby'
 document = LibXML::XML::Document.new
 ```
 
-```ruby
-# Convenience - mixes LibXML into the global namespace
-require 'xml'
-document = XML::Document.new
-```
+If you prefer shorter names, include the LibXML module in your own namespace:
 
 ```ruby
-# In your own namespace
 require 'libxml-ruby'
 
 module MyApp