Show anchor links for each heading

[damithc]

Suggested by a user of CS2103 website nus-cs2103-AY1819S1/forum#15:

Something like in https://developers.timekit.io/v2/reference#section-app-specific-requests

The anchor icon appears on hover in the website but you can implement it as a button or a link.

Occasionally, I feel the need to share specific section of the page to my team.

[damithc]

The feature is working under normal circumstances. 👍
What about cases where the title of a panel is a heading?