resolve #3851 by updating Lua Forms Documentation

[j-ac]

Relevant functions gain notice that x and y must be supplied together.

Also standardize some style conventions that seemed to exist but were not regularly followed. Namely:

• Return value information always follow argument information
• Arguments use consistent capitalization even at start of a sentence
• Bullet points do not end with periods

• I have run any relevant test suites
• I, the committer, have read the licensing terms for contributors (last updated 2022-07-15) and am compliant

[YoshiRulz]

s/specified/not nil/

Also I was going to add a print when only one of the pair is given. I'll do that if you don't want to.

[j-ac]

Also I was going to add a print when only one of the pair is given. I'll do that if you don't want to.

I'll handle the prinout. What exactly did you mean by the following? Should the language in the docs change?

s/specified/not nil/

[YoshiRulz]

Yes. Since you could "specify" nil explicitly.