Added support of Subscription in MetadataParser

[marcinjagielnicki]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Documented?	no
Fixed tickets
License	MIT

Before this change Root Type: Subscription wasn't correcly recognised during metadata parsing while using PHP Annotations/Attributes

[Vincz]

Hi @marcinjagielnicki !
Just a question to better understand your use case. How would you implement the realtime subscriptions?

[marcinjagielnicki]

Hey @Vincz,
I'm already working on a bundle that I can consider as working. It's using mercure protocole as a async communcation channel.
In next weeks my bundle will be ready to be published as public composer package :)

[Vincz]

@marcinjagielnicki Ho, really nice. Can't wait to see this! Could definitively use it on a bunch of my projects.
About your PR, is it everything you need to make your bundle work with this one?

[marcinjagielnicki]

@Vincz at this moment yes, if I will need any other changes I will make separated PR