Provide a better error for positional content

lib/phlex/html.rb

@@ -130,7 +130,11 @@ def register_element(element, tag: element.name.tr("_", "-"))
 			class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
         # frozen_string_literal: true
 
-        def #{element}(**attributes, &block)
+        def #{element}(content = nil, **attributes, &block)
+					if content
+						raise ArgumentError, %(👋 You can no longer pass content to #{element} as a positional argument.\n Instead, you can pass it as a block, e.g. #{element} { "Hello" })
+					end
+
           if attributes.length > 0
             if block_given?
               @_target << "<#{tag}" << (Phlex::ATTRIBUTE_CACHE[attributes.hash] || _attributes(attributes)) << ">"