command line Argument support for both yarn and npm (#629)

* Adding NPM/YARN compatibility to command line args

* added command line param note

* Update dev-runner.js

Improve formatting

* Remove end of file newline

Remove automatically inserted newline at end of file

Author: jeeftor

docs/en/npm_scripts.md

@@ -10,6 +10,10 @@ Build your app for production and package. More info can be found in the [**Buil
 
 Run app in development.
 
+You can also pass command line paramaters to the application with: 
+
+    npm run dev --arg1=val1 --arg2
+
 ### `npm run lint`
 
 Lint all your `src/`'s and `test/`'s JS & Vue component files.

template/.electron-vue/dev-runner.js

@@ -114,8 +114,20 @@ function startMain () {
 }
 
 function startElectron () {
-  electronProcess = spawn(electron, ['--inspect=5858', path.join(__dirname, '../dist/electron/main.js')])
+  var args = [
+    '--inspect=5858',
+    path.join(__dirname, '../dist/electron/main.js')
+  ]
+
+  // detect yarn or npm and process commandline args accordingly
+  if (process.env.npm_execpath.endsWith('yarn.js')) {
+    args = args.concat(process.argv.slice(3))
+  } else if (process.env.npm_execpath.endsWith('npm-cli.js')) {
+    args = args.concat(process.argv.slice(2))
+  }
 
+  electronProcess = spawn(electron, args)
+  
   electronProcess.stdout.on('data', data => {
     electronLog(data, 'blue')
   })
@@ -175,4 +187,4 @@ function init () {
     })
 }
 
-init()
+init()