📝 Fix code style issue

* Match equality operators for consistent that `==`, `!=` by `===`,
`!==`.
* Match string expression notation `"` by `'`.

[ci skip]

docs/api/desktop-capturer.md

@@ -10,7 +10,7 @@ var { desktopCapturer } = require('electron');
 desktopCapturer.getSources({types: ['window', 'screen']}, (error, sources) => {
   if (error) throw error;
   for (var i = 0; i < sources.length; ++i) {
-    if (sources[i].name == "Electron") {
+    if (sources[i].name === 'Electron') {
       navigator.webkitGetUserMedia({
         audio: false,
         video: {