Add scrolling to RHS sidebar

[Paul-Haley]

The sidebar on the right-hand-side (RHS) which contains the Contents list (section titles) is not scrollable. This is an issue for pages that have many section titles as the entire list isn't displayed without scrolling to the bottom of the page; AIP-9 is a good example of this.

Proposal is to make the RHS sidebar scrollable similar to the LHS sidebar (that contains the list of all AIPs).

I was able to produce this issue in Firefox and Safari.