✨ Adds feature that allows to prefer a provider

[mcarlett]

In case of multiple provides found in class path, instead of picking first, it is possible to prefer one using system property slf4j.preferred.provider, providing the claas name

example:
-Dslf4j.preferred.provider=ch.qos.logback.classic.spi.LogbackServiceProvider will pick the instance of this type if present in the list of the identified providers, instead of first one in the list