Docs: improvements for "references - phpdoc - tags - author"
Docs: improvements for "references - phpdoc - tags - author"

Description:
* Mention both RFC 5322 as well as RFC 2822.
    This document originally referred to RFC 5322, while PSR 19 refers to RFC 2822.
    As RFC 5322 supersedes RFC 2822, RFC 5322 would seem the most correct, however, then the text would contradict PSR 19.
    So, for now, I've elected to mention both. I imagine it might be an idea to send in a PR to PSR 19 to update the RFC reference.

Effects in phpDocumentor:
* Minor clarification about the linking.

Other:
* Minor inline markup and grammar fixes.
* Made the syntax outline a code block.
* Collected external links at the bottom of the document.

Ref: https://github.com/php-fig/fig-standards/blob/master/proposed/phpdoc-tags.md#52-author

**Open question**:

I wonder if the "Effects in phpDocumentor" section is still correct as in the current "Default" template, I don't see any `@author` tags displayed.
* Is this on the to do list ?
* Is this no longer supported ?
* Should the section text be updated ?
* Should an issue be opened about support for this tag in phpDocumentor 3 ?

phpDocumentor/phpDocumentor2,phpDocumentor/phpDocumentor2,phpDocumentor/phpDocumentor2,phpDocumentor/phpDocumentor2