Plugin/man: Add R to $LESS

[gaelicWizard]

Description

Add R to $LESS, which is interpreted as flags on the command line. Alsö, don't clobber user-set variables.

Motivation and Context

Otherwise, -R must be added on the command line or colors just won't be rendered and these variables will be ignored. Usually, less gets aliased or wrapped in a function, but if it's not then we'd like to use our settings. This alsö reduces the need to alias or wrap less and is much less likely to break.

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the code style of this project.
• If my change requires a change to the documentation, I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• If I have added a new file, I also added it to clean_files.txt and formatted it using lint_clean_files.sh.
• I have added tests to cover my changes, and all the new and existing tests pass.