Make more clear ISCC is based on content and metadata

[nichtich]

The specification states "An ISCC can be created from digital content and its basic metadata". The "How it works" section at https://iscc.codes/ is misleading about this because it does not mention metadata:

ISCC identifiers are generated algorithmically from the content itself. Content files are processed to build the identifier

The image below could be read as if metadata is part of the content. "Content" is also used to differentiate "Meta", "Content", "Data", "Instance". Maybe have some more clear definition of "content": does it subsume metadata or not?