Documentation: collect everything you can do with NgxExtendedPdfViewerService on a single page

[stephanrauh]

When answering #1884, I noticed that

• the showcase page "Editor API (settings)" only list a few - but not all - methods, so the reader needs to guess which method they have to call to implement some of the features shown in the demo
• the page "attribute and events" doesn't list these method, either.

To solve that, I'd like to

• add the code snippet behind the input fields of the live demo of the "Editor API (settings)" page
• and add a third tab to the "attribute and events" tab that collects all the features provided by NgxExtendedPdfViewerService.