Add PHP Doc to every public method of T-Regx API

[danon]

• Include a detailed documentation of every public method
• Include only @param, @returns and @throws tags.
• Include @psalm and @phpstan annotations
• Include @see and @link attributes linking to classes and documentation on t-regx
• Add @api tag to public elements and @internal tag to implementation details (most of Internal/ namespace)

[danon]

This will be done with https://github.com/T-Regx/documentary

[danon]

PhpDocumentor is wierd, for example it understands HTML both in summary and description; but only understands markdown in summary, and not in the description.