move latex special characters text to wiki or latex training

[mariaruth]

This sentence is too granular to fit in the book IMHO. And if we should keep it we should not keep it in a cloud specific section. We could perhaps move it next to `what-you-see-is-what-you-get' around line 127, as an example when what you see is what you get does not apply.

Originally posted by @kbjarkefur in https://github.com/worldbank/d4di/diffs

move this sentence to wiki or latex training:

A common problem you will face using online editors is special characters which, because of code functions, need to be handled differently than in Word. Most critically, the ampersand (\texttt{&}), percent (\texttt{%}), and underscore (\texttt{_}) need to be ``escaped'' (interpreted as text and not code) in order to render. This is done by by writing a backslash (\texttt{\textbackslash}) before them,
such as writing \texttt{40\textbackslash%} for the percent sign to appear in text.

[kbjarkefur]

Will do this. Tried to do it this morning but github was acting up