helpview: Introduce scroll-bar for scrolling through HelpView.
This is more of a food for thought PR (hence the 'draft') in hopes that it may possibly be an option we may want to consider one day. This introduces the feature of having a scroll-bar in ListBox's whose purpose would be to
- Aid navigation (UX wise).
- Give a visual sense of 'how much more' there is to scroll.
- Possibly avoid the Up/Down in the title.
As it stands the feature isn't implemented yet in urwid and has been adapted from https://github.com/rndusr/stig/blob/master/stig/tui/scroll.py.
A screenshot of this implemented on the HelpView, looks as follows:

An alternative to this may be something like this https://github.com/AFoeee/additional_urwid_widgets/wiki/IndicativeListBox, though that does use space at the top and bottom.
Heads up @sumanthvrao, we just merged some commits that conflict with the changes your made in this pull request! You can review this repository's recent commits to see where the conflicts occur. Please rebase your feature branch against the upstream/master branch and resolve your pull request's merge conflicts accordingly.