Add Doctrine Field Types Reference

[Mynyx]

Regarding the available field types, the Databases / Doctrine documentation (https://symfony.com/doc/current/doctrine.html) contais only a reference to the Doctrine documentation:

Doctrine supports a wide variety of field types, each with their own options. Check out the list of Doctrine mapping types in the Doctrine documentation.

This does not include the additional field types in the Symfony\Bridge\Doctrine\Types namespace.

Therefore a Doctrine Field Types Reference seems sensible as an addition to the documentation. This could also include information on choosing between similar field types.