docs(): viewport should be not scalable (#9490)

* Normally modern webapp do not allow the developer to zoom into the page on mobile.
  This applies the most common meta tag to the docs page and makes the demos look way better on mobile.

* Components, which have a text input (like datepicker, autocomplete or normal input) no longer zoom in, when clicking on them.

Author: devversion

docs/config/template/index.template.html

@@ -7,7 +7,7 @@
   Angular Material
 </title>
 <link rel="icon" type="image/x-icon" href="favicon.ico" />
-<meta name="viewport" content="initial-scale=1" />
+<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no">
 <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Roboto:300,400,500,700,400italic">
 <link rel="stylesheet" href="angular-material.min.css">
 <link rel="stylesheet" href="docs.css">