to introduce some styling changes to make the desktop view more clean and accurate w.r.t. UI/UX perspective

[Shubhambawner]

Is your feature request related to a problem? Please describe.
for Desktop view, left navigation pane and document text together give it a little messy feel
I want to introduce some styling changes to make the desktop view more clean and sophisticated.
For elaboration, here is what currently looks like:

source : https://dev3.atsign.wtf/sdk/java/introduction/
Notice how the left navigation pane and document text are bumping into each other?
Altogether it fails to match neat and clean design, several other documentations can be referenced here for example:

Describe the solution you'd like
following re the changes I wish to perform:

• add appropriate spacing between left and right column.
• add line height to the text in left navigation pane
• limit the width of readable document, to ease out the reading process

Describe alternatives you've considered
Currently I see the above only as some good solution, suggestions welcome

Additional context
We can move ahead with modifications and enhancements later.

[Shubhambawner]

I would be grateful if this Issue gets assigned to me along with the hacktoberfest label!