Allow setting field boosts through Settings.yaml

[Benjamin-K]

In the "original" Flowpack.ElasticSearch.ContentRepositoryAdaptor-Package, you can set the boost through Settings.yaml.

Is it possible to use this configuration instead of setting it directly in the php code?

Either we could adopt the existing settings of the Flowpack.ElasticSearch.ContentRepositoryAdaptor and override them in this package, or we could add new settings.

I think this would help improving search for some people.

(BTW: I can create a PR, but I need a decision which option to use: Own settings or existing ones)