Add Ruby 3.2 support

Rakefile

@@ -12,11 +12,9 @@ task build: :compile
 ext_dirs = %w[decoders/native decoders/crunch]
 
 ext_dirs.each do |dir|
-  Rake::ExtensionTask.new(dir) do |ext|
-    ext.lib_dir = 'lib/mikunyan'
-  end
+  Rake::ExtensionTask.new(dir)
 end
 
-task compile: ext_dirs.map{|e| "compile:#{e}".to_sym}
+task compile: ext_dirs.map {|e| "compile:#{e}".to_sym}
 
 task default: %i[clobber compile spec]