doc: fix issues related to page scrolling (v4.x backport)
Backport of https://github.com/nodejs/node/pull/6641/commits/15df52ab3d82e0a55ed2875f654fa92e46f81f38 to v4.x, hope I'm doing this right. It's a straight cherry-pick.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Backport of https://github.com/nodejs/node/pull/6641/commits/15df52ab3d82e0a55ed2875f654fa92e46f81f38 to v4.x, hope I'm doing this right. It's a straight cherry-pick.