Code style and formatting in the documentation

[artifex404]

PHP, Twig and HTML code should be written in one concise format and styling in the documentation. As of now, there is a lot of variations.

I thought about contributing with the clean up, but wanted to ask first a more official opinion which style/formatting to apply.

[jarednova]

@artifex404 that would be very helpful. A lot of hands over the years (including mine) have been in there over the years with some changing rationales. This describes the PHP rules (from Scrutinizer CI). In general, it's pretty close to WordPress's official standards.

For Twig and HTML, I'd like to stick to the official Twig standards where we can

[nlemoine]

Since 2.x and code standards auto fixing implementation (including docs snippets), I think we can close this.