:dfn[foo] should be presented in a way that allows for linking to them

[lidel]

Currently, it is not possible to copy link to specific definition, even tho each have own anchor, and we link to them:

(example from ipfs/specs#390)

Quick ideas:

• style :dfn[ so we can spot them? (dotted underline? Italic font? different weight?)
• on :hover show <a> as # on the left (similar to how we already expose links to headers, but hide them by default)

cc @darobin @hacdias thoughts / ideas / examples how we could present this better?

[hacdias]

Perhaps dotted underline could be an idea?