Add glossary to introductory or popular articles

[texasdiaz]

JoAnn would like for us to consider adding a glossary to introductory and popular articles for new readers to reference, for instance "Op Mode" isn't always defined in introductory articles.

[Danny] Consider possibly adding hoverxref plugin to create hover-items for glossary terms.
https://sphinx-hoverxref.readthedocs.io/en/latest/usage.html

[WestsideRobotics]

PR from @uvidyadharan called "Add Glossary":

#237