Support SLF4J 2.x

[halotroop2288]

I would love to continue using this for my standalone projects, but it seems it doesn't work with the latest version of SLF4J anymore. (It works up to release 1.7.36)

SLF4J: Class path contains SLF4J bindings targeting slf4j-api versions 1.7.x or earlier.
SLF4J: Ignoring binding found at [jar:file:/C:/Users/Administrator/.gradle/caches/modules-2/files-2.1/com.unascribed/asyncsimplelog/4.6.1/595cef5f31034056525f39639f19256c2b7b0bf2/asyncsimplelog-4.6.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See https://www.slf4j.org/codes.html#ignoredBindings for an explanation.

[unascribed]

I'm aware but thus far haven't cared, as I prefer the static binder system used by pre-2.0 SLF4j. The modern system may be Java-native but it's as overengineered as Log4j was.

There's very little new API in 2.0, you can generally force a 1.7 dependency and things will work, which is what I've been doing.