Add functions that checks the log level desired

[aleal]

The functions will return true if log level is enabled I.e:
log.IsDebug() // returns true for trace and debug levels
log.IsTrace() // returns true for trace level
log.IsInfo() // returns true for trace, debug and info levels

// may a enum could be added to simplify those checks

this will help to avoid doing unnecessary, and maybe expensive, operations, for example, marshalling an object, or doing a reflection to check some condition or something else in debug mode.

[jpfaria]

I totally agree.

however, there are cases like logrus where you can have specific configuration per output. How would we solve this scenario?