[Contact] Added simple contact form managing

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Fixed tickets |
| License       | MIT
| Doc PR        | Sylius/Sylius-Docs#215
We could, but we do not do this anywhere else, so I guess it is ok! :)