Document the new behaviour of JxlDecoderReleaseInput.
Document the new behaviour of JxlDecoderReleaseInput.

Added documentation to each informative event as to where the
input processing stops and how many unprocessed bytes are
returned by JxlDecoderReleaseInput.

libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl