refactor: app.parseAndTranslate to return promise if no callback passed

public/src/app.js

@@ -736,21 +736,29 @@ app.cacheBuster = null;
 	};
 
 	app.parseAndTranslate = function (template, blockName, data, callback) {
-		require(['translator', 'benchpress'], function (translator, Benchpress) {
 		if (typeof blockName !== 'string') {
 			callback = data;
 			data = blockName;
 			blockName = undefined;
 		}
 
+		const execute = (resolve, reject) => {
+			require(['translator', 'benchpress'], function (translator, Benchpress) {
 				Benchpress.render(template, data, blockName)
 					.then(rendered => translator.translate(rendered))
 					.then(translated => translator.unescape(translated))
-				.then(
+					.then(resolve, reject);
+			});
+		};
+
+		if (callback) {
+			execute(
 				result => setTimeout(callback, 0, $(result)),
 				err => console.error(err)
 			);
-		});
+		} else {
+			return new Promise(execute).then(html => $(html));
+		}
 	};
 
 	app.showCookieWarning = function () {