[PSR-12] / PR for small updates.

[William Pinaud]

Hey there, sorry to kick in out of nowhere, but I just thought I could do a little regarding PSR-12.

Not really willing to change its contents, I do like it in general, but I'm usually rather... Meticulous, if not psychorigid.
I did a lot of grammar updates regarding "perfecting" the markdown syntax last year, for PSR 13/14/17.

This time, I did open a PR for 12.

https://github.com/php-fig/fig-standards/pull/1183

The edit list goes as follows:

• wording/grammar
• new lines coherence
• examples enrichment matching given enumerated domains of application
• italics for word reference quoting
• added exceptions for HEREDOC/NOWDOC to trailing spaces
• switched to ordered list for PHP header file order listing to better reflect ordering
• updated wording to better reflect internal references
• added proposed complements for unary operators needing clarification (especially regarding the ambigous "- $a" / "-$a")

I didn't change the background contents, but mostly added coherence regarding syntax and PHP examples.

Mostly to have concerned PHP domains listing matching examples, and adding a few exceptions, for PSR-12 goes deeper into PHP-specific syntax.

Hope I'm going to help. :)

[Alexander Makarov]

Thank you!