Add some linting rules for the CI (#587)

* enable one-var rule

* enable indent rule

* enable no-multiple-empty-lines rule

* enable no-empty rule

* enable no-trailing-spaces rule

* enable no-extra-semi rule

* add eslint rules to fix block spacing

* enable max-statements-per-line rule

* enable brace-style rule

* fix some spacing issues and add future rules

* add code suggestions

src/bundle.js

@@ -6,59 +6,87 @@ var _define = window.define;
 
 // document-register-element
 var docRegister = require("document-register-element");
-_define("document-register-element", function() { return docRegister; });
+_define("document-register-element", function() {
+    return docRegister;
+});
 
 // fetch
 var fetch = require("whatwg-fetch");
-_define("fetch", function() { return fetch });
+_define("fetch", function() {
+    return fetch
+});
 
 // flvjs
 var flvjs = require("flv.js");
-_define("flvjs", function() { return flvjs; });
+_define("flvjs", function() {
+    return flvjs;
+});
 
 // jstree
 var jstree = require("jstree");
 require("jstree/dist/themes/default/style.css");
-_define("jstree", function() { return jstree; });
+_define("jstree", function() {
+    return jstree;
+});
 
 // jquery
 var jquery = require("jquery");
-_define("jQuery", function() { return jquery; });
+_define("jQuery", function() {
+    return jquery;
+});
 
 // hlsjs
 var hlsjs = require("hls.js");
-_define("hlsjs", function() { return hlsjs; });
+_define("hlsjs", function() {
+    return hlsjs;
+});
 
 // howler
 var howler = require("howler");
-_define("howler", function() { return howler; });
+_define("howler", function() {
+    return howler;
+});
 
 // native-promise-only
 var nativePromise = require("native-promise-only");
-_define("native-promise-only", function() { return nativePromise; });
+_define("native-promise-only", function() {
+    return nativePromise;
+});
 
 // resize-observer-polyfill
 var resize = require("resize-observer-polyfill");
-_define("resize-observer-polyfill", function() { return resize; });
+_define("resize-observer-polyfill", function() {
+    return resize;
+});
 
 // shaka
 var shaka = require("shaka-player");
-_define("shaka", function() { return shaka; });
+_define("shaka", function() {
+    return shaka;
+});
 
 // swiper
 var swiper = require("swiper");
 require("swiper/dist/css/swiper.min.css");
-_define("swiper", function() { return swiper; });
+_define("swiper", function() {
+    return swiper;
+});
 
 // sortable
 var sortable = require("sortablejs");
-_define("sortable", function() { return sortable; });
+_define("sortable", function() {
+    return sortable;
+});
 
 // webcomponents
 var webcomponents = require("webcomponents.js-2");
-_define("webcomponents", function() { return webcomponents });
+_define("webcomponents", function() {
+    return webcomponents
+});
 
 // libjass
 var libjass = require("libjass");
 require("libjass/libjass.css");
-_define("libjass", function() { return libjass; });
+_define("libjass", function() {
+    return libjass;
+});