Document what TypeResolver does with nullable types

[TysonAndre]

https://github.com/phpDocumentor/TypeResolver/pull/35/files implemented support for these, but does not mention "nullable" anywhere in the README.md of this project.

Questions I have:

• Could you update the README to mention where nullables are supported?
• Is phpdoc nullable supported? (No movement in http://www.php-fig.org/psr/ PSR-5 lately)
• If it is, add integration tests to make the supported locations clear? (e.g. parsing /** @param ?int $x*/ function test($x);)

[jaapio]

I added the missing chapter to the Readme.

phpdoc will support nullable in the future. We started a new working group to continue the work on PSR-5.
This library only resolves the types. It doesn't parse docblocks. Have a look at https://github.com/phpDocumentor/ReflectionDocBlock to see how to parse docblocks.