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

Description:
* Combined existing text with the current description in PSR-19 with minor adjustments for clarification.

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

Example:
* Synced the examples with the current examples in PSR-19 (non-inline).
* Made the inline example use a fully qualified class name to demonstrate that that is a valid way to use this tag.
* Modernized the Type used in the `@return` tag.

Other:
* 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 (which in this case was prevented previously by the backslash, which is now no longer necessary).
* Collected external links at the bottom of the document.

Ref: https://github.com/php-fig/fig-standards/blob/master/proposed/phpdoc-tags.md#512-see

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