for better mobile/small form factor support (eg when using landscape) - don't specify the device-width etc
(see e.g. https://developer.apple.com/library/content/documentation/AppleApplications/Reference/SafariWebContent/UsingtheViewport/UsingtheViewport.html )

Replaces the need for `$this->data['htmlinject']`

Note that the flag in the context must be named 'clipboard',
not 'clipboard.js'. This is because the dot is an illegal symbol in
variable names in twig.