Suggestion for improvement in the docs/PDFs

[kolban]

I'm not sure how to describe this ... so I'll use a lot of words.

When I open the SDK API PDF, I use the Adobe Acrobat Reader. In the left, there is a place where one can see all the major headings in a PDF ... normally. However, the ESP8266 doc, there are no headings ... only thumbnails of the pages. As such, when I want to go to a particular section or page, I have to search or scroll. In addition, I seem to find that the table of contents at the start of the document are not "hyperlinked". What I mean by this is that when I click on a section in the table of contents, I expect to be jumped to that section. Today, nothing happens.