Create Log4J, Log4J2 and JUL appenders

I'll be happy to contribute the code if interested.

Review the existing fluent-logger-java structure and current logging integration first; no implementation files or tests are identified in the issue. Clarify the expected scope and behavior for Log4J, Log4J2, and JUL appenders, then define completion as working integrations for all three with appropriate tests.

索引モデルが issue の本文から書いたものです。