Punctuate marketing headings with a period. Fix a couple of title-cased headings to sentense case. Consistently use curly apostrophes, curly quotation marks, and Unicode ellipses. Signed-off-by: Anders Kaseorg <anders@zulipchat.com>
I guess these pages are not covered by tools/test-documentation.
This restyles them to be more readable and more put together than before by changing the line heights, text colors, and padding.