Have an indentation guides option

## Problem

Some times extraneous spaces get inserted at the start of lines when cutting and pasting from another source. It is then hard to tell which lines are correctly indented by a multiple of 4 spaces.

## Proposal

Vertical dotted lines at the correct tab spacing in the space preceding indented lines would be useful for detecting extraneous spaces.

## Prior Art

Other IDEs like Geany implement this
You can easily see in the example that there is an extraneous space before a closing brace.