Add doctrine/annotations dependency

[Koc]

see
symfony/symfony#20097
symfony/recipes-contrib#22 (comment)

[harmstyler]

Is this necessary as a required dependency? Due to the fact that Annotations are optional for this bundle the annotations library should be optional as well. I'd recommend a composer suggestion over a requirement:

"suggest": {
    "doctrine/annotations": "To use Symfony annotations."
}

[garak]

I agree.
Likely we'll need a line in "require-dev" also

[Koc]

Doctrine is a first-class citizen. Adding this dependency as required helps us avoid many missunderstandings and issues in future.

[garak]

I think it's just a matter of begin clear in docs.
Even if annotations are suggested in first place, they're not technically a requirement

[Koc]

Some parts of DI should be rewrited. Currently annotations are required by code, see symfony/recipes-contrib#22 (comment)

[garak]

If so, annotations are actually a requirement.