Improve page navigation

[nbhuiyan]

This issue is to track improvements/fixes to the base9 Developer Journey navigation menu.

An inspiration of how the final developer journey document page could look like is Bootstrap's own documentation site:
https://getbootstrap.com/docs/4.1/components/navbar/

Here is a list of improvements/fixes that are to be made to achieve something similar to the above example:

• Fix: Jumping to sections from the side navigation bar jumps to a point where the section title is covered by the top navigation bar.
• Auto-generate page navigation menu items. It is currently manually coded, which is very tedious to maintain.
• Break the different sections into multiple pages instead of one very long page
• Make the sections/subsections in the side navigation bar highlight the current section and subsection on display.
• For smaller screens, make the side navigation bar collapse by default and form a horizontal expandable menu bar under the top navigation bar.
• For smaller screens, do not have any of the navigation menu bars follow the current view