Comb through reference documentation and fix small typos

[stylewarning]

The reference documentation has a decent number of typos and inconsistencies. For example, inconsistencies in how variables are referenced:

(define (f x) x)

may be documented as:

• The function F calculates the variable X.
• The function`f' calculates the variable `x'.
• The function f calculates the variable x.

The third one is the correct one.

[stylewarning]

overly eager HTML escaping in Markdown code blocks also happens; example here: https://coalton-lang.github.io/reference/#quantizable-class

[jbouwman]

overly eager HTML escaping in Markdown code blocks also happens; example here: https://coalton-lang.github.io/reference/#quantizable-class

This part has been fixed by #1166