Document "layers" and "title"

[LaCivette]

I found the meaning of those options here: https://www.diagrams.net/doc/faq/embed-html-options

I have only tested "layers" and "title".

Please make sure these boxes are checked before submitting your PR

• [ x] Make sure local test / build is ok
• [ x] Make sure ts type complete
• [ x] add necessary comments

[xiguaxigua]

Thank you for the information you provided, I will test the relevant fields in the near future and add them to the document