document viewport suggestions

[pkra]

See https://groups.google.com/d/msg/mathjax-users/CFhPmGixWWE/M8vflfqdCw0J

<meta name="viewport" content="width=device-width,minimum-scale=1.0, maximum-scale=1.0" />

[pkra]

Following https://developers.google.com/web/fundamentals/layouts/rwd-fundamentals/set-the-viewport, maybe rather
<meta name="viewport" content="width=device-width,minimum-scale=1.0, maximum-scale=1.0" />

[pkra]

Oops, sorry, I meant <meta name="viewport" content="width=device-width, initial-scale=1">