Add guidance on use of "while"

[julian-cable]

Guidance to add:
In technical content, use “while” only to indicate that many tasks or processes occur at the same time.

Original example:
"While most targets use one target portal group (TPG), advanced configurations might define multiple TPGs."

Improvement example:
"Although most targets use one target portal group (TPG), advanced configurations might define multiple TPGs."

[julian-cable]

Added guidance and examples to usage dictionary.