Add basic escape when ERB not defined

lib/phlex.rb

@@ -10,6 +10,14 @@ module Phlex
 	#  rescue Phlex::Error
 	module Error; end
 
+	if defined?(ERB::Escape)
+		Escape = ERB::Escape
+	elsif defined?(ERB::Util)
+		Escape = ERB::Util
+	else
+		Escape = BasicEscape
+	end
+
 	# A specialised ArgumentError for Phlex.
 	class ArgumentError < ::ArgumentError
 		include Error

lib/phlex/basic_escape.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Phlex
+	module BasicEscape
+		def html_escape(string)
+			string
+				.dup
+				.gsub!("&", "&")
+				.gsub!("<", "&lt;")
+				.gsub!(">", "&gt;")
+				.gsub!('"', "&quot;")
+				.gsub!("'", "&#39;")
+				.freeze
+		end
+	end
+end