[latexrefman] Add section on math styles

[Hefferon, Jim S.]

I added a section, expanding the coverage of the declarations from just \displaystyle and \textstyle to include \scriptstyle and \scriptscriptstyle.

Jim

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"The president bears responsibility for Wednesday's attack on Congress by mob rioters. He should have immediately denounced the mob when he saw what was unfolding ... And, a fact-finding commission would be prudent." -- Kevin McCarthy, January 13, 2021