Recommend never using clean task

[lacasseio]

Let's create an FYI entry on why clean tasks should mostly never be used.

[lacasseio]

It's important for users to understand that clean is an error (philosophically). We should never have to rebuild or simply clean. Given that build-cache should be enabled by default, execution like ./gradlew clean assemble should simply restore from the cache, hence unless. It also shows a lack of confidence in the tools which should be addressed at its core, by opening issues on the Nokee or Gradle repositories clearly stating the concerns so we can provide the necessary documentation/data/research to clarify any confusion around using clean.

Aside from the FYI entry, we may explicitly warn users when clean task is invoked pointing to this entry to ensure clean task is properly used.