support html5 embedded font input text via @font-face

basic implementation based on suggestions by glantucan. for it to work, the font (ttf) files need to be copied into the build folder (with something like <assets path="assets/font" rename="font" />). for this to work i commented out lines 138 and 143 of src/platforms/HTML5Platform.hx in hxtools (1.1.6), which is part of openfl. removing the comments from lines 20 and 24 in helpers/HTML5Helpers.hx also helps...