feat: add ConsoleLogger

feat: envvar & per target log level setting (#1)

* chore: rename base method name BREAKING CHANGE: public member changed
* feat: add "max_level" setting for target level
* feat: easy interop with V's `log` module
* feat: enable to use custom envvar

feat: simple log fn support `target` as 1st arg

BREAKING CHANGE: simple log fn requires 2 args

chore: add version & description