[manual of style] Describe how styling works, and point to examples

[nigelmegitt]

I just scanned through the Manual of Style thinking that it might tell me about styling, and discovered that it only mentions CSS in a few places, and doesn't do some things that I think could be helpful:

1. Explain how styling is applied by default, i.e. that there's a W3C stylesheet, and a fixup script
2. Note that it doesn't cover everything, and how to add more styling - is it better to include inline styling or reference an additional stylesheet? (I've always added an inline style block, but maybe people have other opinions!)
3. Include some pointers to examples where folk have worked around practices or Process requirements that the stylesheet doesn't (yet) support, for example:
   a. indicating embedded Registry sections. e.g. in DAPT's two registry sections (such as <content-descriptor>);
   b. styling the "Tests" details sections e.g. in CSS Fonts Level 4);
   c. indicating features that contribute to fingerprintability (PING Fingerprinting Guidance best practice 3)