Consider documenting difference between two usages

[oliviercailloux]

Is your feature request related to a problem? Please describe.
I see (at least) two ways of using Vnu as an embedded library.

• At SO you gave a simple way of using the validator directly through jing (as embedded in vnu.jar), that boils down to a few simple lines of code. This seems to work.
• OTOH, “unwrapping” the code from SimpleDocumentValidator leads to some apparently much more complicated usage, involving setting system properties, using cascading schema instances and validators and xml readers interacting with a SourceCode instance, …

Describe the solution you'd like
Please document briefly how these two approaches differ, in view of providing an as-correct-as-possible validation of (X)HTML documents.

Describe alternatives you've considered
#71 is about extending the README about instructions for using the validator as an embedded library. I had initially posted the current question in that thread. However, my request (slightly) differs as I do not want a nice and clear documentation to appear in the README (which I believe you might not have time to provide anytime soon), but just a bit of targeted help in view of me developing a wrapper and making sure it works correctly. Therefore, I hope that it is more appropriate to post my question as a new thread in order not to hijack the one about the README. I do not want to mislead users by letting them believe that invalid documents are valid, so I want to make sure that I am calling the library correctly.

Additional context
I intend to publish this wrapper as an open source project so that others can benefit. The wrapper I intend to build differs from the EmbeddedValidator one (#1265) on two aspects.

• It intends to provide an approach compatible with SAX for easy combination with code that validates other kinds of documents.
• It intends to provide a more programmer friendly approach to validation (a need that is highlighted here).