In window.searxng.theme the theme data can be passed through to JS
implementations.
Initial the window.searxng.theme namespace starts with a value for
`img_load_error`::
// image that is displayed if load of <img src='...'> failed
img_load_error: 'img/img_load_error.svg'
The searx/static/themes/__common__/js/image_layout.js is patched to uses the
value, if the theme defines a value for img_load_error in this namespace.
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
When an image is selected, the detail with the full size image is displayed
on the right side of the screen (or full screen on tablet and phone).
When Javascript is disabled, the thumbnail is a linked to the full size image,
as it was before.
When the image proxy is enabled, the full size image is also proxied,
in consequence this commit increases the bandwidth usage of instances.
The detail can be closed by the close button or the Esc key.
It is possible to go to the next and previous images using the j and k keys
or the button on the top right of the screen.
