Add a CSS class to the HTML tag

var img = new HTMLTag("img")
img.add_class("logo").add_class("fullpage")
assert img.write_to_string      == """<img class="logo fullpage"/>"""

Property definitions

html $ HTMLTag :: add_class
	# Add a CSS class to the HTML tag
	#
	#     var img = new HTMLTag("img")
	#     img.add_class("logo").add_class("fullpage")
	#     assert img.write_to_string      == """<img class="logo fullpage"/>"""
	fun add_class(klass: String): HTMLTag do
		classes.add(klass)
		return self
	end
lib/html/html.nit:153,2--161,4