Add app.fullscreen module to handle virtual "fullscreen" of app content

web/src/app/js/app.js

@@ -245,6 +245,21 @@ app.post = {
 	},
 }
 
+app.fullscreen = {
+	enable: function() {
+		const el = document.querySelector('main');
+		el.classList.add('absolute-top');
+		el.classList.add('width-max');
+		document.querySelector('header').style.display = 'none';
+	},
+	disable: function() {
+		const el = document.querySelector('main');
+		el.classList.remove('absolute-top');
+		el.classList.remove('width-max');
+		document.querySelector('header').removeAttribute('style');
+	},
+}
+
 app.media = {
 	view: function(url) {
 		if (url.match(/^.*\.(jpg|jpeg|png|ico|webp)$/))
@@ -484,6 +499,7 @@ window.onhashchange = function(e) {
 		args = [];
 
 	app.overlay.hideAll();
+	app.fullscreen.disable();
 	for (var i = 0; i < app.hashHandlers.length; i++) {
 		const cfg = app.hashHandlers[i];
 		if (cfg.exact !== undefined &&

web/src/app/js/pages/quiz.js

@@ -13,6 +13,7 @@ app.pages.quiz = {
 			}
 		}
 
+		app.fullscreen.enable();
 		const container = document.getElementById('app-container');
 		container.innerHTML = '';