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

Summary:
* Moved the note about support in phpDocumentor to the "Effects in phpDocumentor" section.

Effects in phpDocumentor:
* Split the text into two paragraphs for improved readability.

Example:
* Modernized the Type used in the `@return` tag.

Other:
* Verified the text with PSR 19.
* Minor inline markup and grammar fixes.
* Made the syntax outline a code block.
    This also fixes the "internal" syntax resulting in an invalid email link.
* Collected external links at the bottom of the document.

Ref: https://github.com/php-fig/fig-standards/blob/master/proposed/phpdoc-tags.md#56-link

**Open question**:

I wonder if the note about support in phpDocumentor (now moved to "Effects in phpDocumentor") is still correct.
* Based on the specs the `@link` tag should only have support for URIs, not FQSEN, so why mention that as missing support ?
* IIRC, both stand-alone as well as inline `@link` tags seem to be supported in phpDocumentor 3, though some tweaking may still be needed, so is this note still relevant at all ?
* And if it is, it may be more helpful to be more specific about what is and isn't supported, so what can you tell me as input to update this ?

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