Allow injecting a custom renderer class

[apauly]

This PR does not really alter the behaviour of the gem, but it allows easier implementation for custom behaviour.

• The component helper optionally accepts a custom renderer class
• The ComponentRenderer itself has been refactored a bit to allow customization of property assignment

Use case: We'd like to use komponent in a setup where we need to customize the property assignment to enable localization (including inline editing). The changes in this PR would implement an interface for customization only - without binding to a special kind of customization.

Note: The .rubocop.yml change is due to a warning by rubocop itself

[Spone]

Thanks @apauly for your contribution. We'll review it shortly.

Would you mind adding documentation about this change in the README?

[apauly]

Hi @Spone ,

sorry for the delayed response - I've now added a section to the README.