added overridable blocks and passing serializing functions as props

[Ducica]

❤️ Thank you for your contribution!

Description

We would like to use the creatibutor component for our apps as well. Generally, we really like the look/functionality. We only have small issue, because it is not possible to make any, relevant customizations. This PR keeps 100% the current behavior of the app. The only change is:

1. Added overridable blocks (for our case, certain things as affiliations for the Organizational type of creatibutors does not make sense).
2. Passing three functions as props (to serializeSuggestions, and to serialize and deserialize creatibutors). These are by default undefined and the ones already existing are used by default.
   The issue can be for example, we have more types of identifiers and also our static folder might have different structure (for icons and such).

We would really appreciate if you would consider merging this. I think it could be beneficial also for other users/partners of invenio.

Please let us know and thank you!

Dusan Stojanovic (CESNET).

[Ducica]

@zzacharo @ntarocco Hey guys, we've made a small PR for the creatibutors component. If it is possible to take a look at it please and let us know if this is something you would consider merging. Even if not, kindly give feedback (yes/no) in any case, as we need to take a different direction if merging this will not be possible. Naturally we would prefer not to have 95% copy of this component ourselves, so it would be really great if we could merge it. Thanks a lot!