qr-code-scanner: port to new qr-scanner v1.4

Multiple changes:

The worker can now be auto-bundled via rollup and no longer has to be passed manually.
This is handled via a js script file which builds a blob containing bundled code.
This requires some CSP exceptions in the target applications, so mention that in the README.

scanImage() now takes an option object and defaults to returning more information, so
handle both changes (returnDetailedScanResult now defaults to true)

Component users can now drop their worker copying code and need to adjust their CSP.