EXIF image orientation can no longer be ignored for cross-origin images

[mzur]

w3c/csswg-drafts#5165 was resolved with a decision that makes it impossible to ignore EXIF image orientation for cross-origin images without CORS.

We decided that we need to disable support for these images as they are (currently) displayed inconsistently across browsers, potentially resulting in invalid annotations. Instead, we will show an error message asking users to enable CORS on their webserver.

[mzur]

I decided to take an iterative approach where we display a prominent warning message but allow users to continue at their own risk. Remote image support without CORS will then be dropped entirely in a future release.