Rewrite the intro to start with examples
Rewrite the intro to start with examples

My experience is most people jump straight to code snippets. Why not start the page with them?

This commit also makes the “Comments” and “Selectors” reference more structured.
- I never, ever realized comments are supported, before. I typically scan the page by looking at its headers, and I think some other people do so as well, so I hope this will help them to realize comments supported.
- I also never had a good idea of what kind of selectors I can use. This expands the section amd (hopefully) makes it easier to scan.

WPO-Foundation/webpagetest-docs,WPO-Foundation/webpagetest-docs