chore(index.html): add charset, prevent scaling, use default attributes (#58)

- Add missing `<meta charset="utf-8">` to `<head>` section
- Add `user-scalable=no` to `<meta viewport>` to prevent users from scaling the app
- Remove unnecessary default type attributes like `type="text/css"`, `type="text/javascript"`
diff --git a/template_src/www/index.html b/template_src/www/index.html
index d901e26..82dbdb4 100644
--- a/template_src/www/index.html
+++ b/template_src/www/index.html
@@ -19,6 +19,7 @@
 -->
 <html>
     <head>
+        <meta charset="utf-8">
         <!--
         Customize this policy to fit your own app's needs. For more guidance, see:
             https://github.com/apache/cordova-plugin-whitelist/blob/master/README.md#content-security-policy
@@ -31,8 +32,8 @@
         <meta http-equiv="Content-Security-Policy" content="default-src 'self' data: gap: https://ssl.gstatic.com 'unsafe-eval'; style-src 'self' 'unsafe-inline'; media-src *; img-src 'self' data: content:;">
         <meta name="format-detection" content="telephone=no">
         <meta name="msapplication-tap-highlight" content="no">
-        <meta name="viewport" content="initial-scale=1, width=device-width, viewport-fit=cover">
-        <link rel="stylesheet" type="text/css" href="css/index.css">
+        <meta name="viewport" content="user-scalable=no, initial-scale=1, width=device-width, viewport-fit=cover">
+        <link rel="stylesheet" href="css/index.css">
         <title>Hello World</title>
     </head>
     <body>
@@ -43,7 +44,7 @@
                 <p class="event received">Device is Ready</p>
             </div>
         </div>
-        <script type="text/javascript" src="cordova.js"></script>
-        <script type="text/javascript" src="js/index.js"></script>
+        <script src="cordova.js"></script>
+        <script src="js/index.js"></script>
     </body>
 </html>