Add --help

Author: ChALkeR

main.js

@@ -1,11 +1,17 @@
 const electron = require('electron');
 const path = require('path');
 const minimist = require('minimist');
+const usage = require('./usage');
 
 const argv = minimist(process.argv.slice(2), {
   boolean: true
 });
 
+if (argv.help) {
+  console.error(usage);
+  process.exit(0);
+}
+
 let argument = argv._[0];
 if (!argument) {
   console.error('Error: No filename specified!');

usage.js

@@ -0,0 +1,6 @@
+module.exports = `Usage: qmlweb-viewer [options] <filename>
+
+ Options
+  --debug .......................... Open Dev Tools window
+  --help ........................... Display help and exit
+`;