Add accessor for the yq logger instance (#1013)

Allow consumers of yqlib to customize the logger instance.

Closes #432

Signed-off-by: Carolyn Van Slyck <me@carolynvanslyck.com>

Co-authored-by: Carolyn Van Slyck <me@carolynvanslyck.com>
Co-authored-by: Rob Ferguson <robert.j.ferguson@nasa.gov>

pkg/yqlib/lib.go

@@ -15,6 +15,11 @@ import (
 
 var log = logging.MustGetLogger("yq-lib")
 
+// GetLogger returns the yq logger instance.
+func GetLogger() *logging.Logger {
+	return log
+}
+
 type operationType struct {
 	Type       string
 	NumArgs    uint // number of arguments to the op