added README

Author: orkunkaraduman

README.md

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+# erf
+
+[![Go Reference](https://pkg.go.dev/badge/github.com/goinsane/erf.svg)](https://pkg.go.dev/github.com/goinsane/erf)
+
+Package erf provides error management with stack trace.
+Erf is an error type that wraps the underlying error that stores and formats the stack trace.
+Please see [godoc](https://pkg.go.dev/github.com/goinsane/erf) and [example](https://github.com/goinsane/erf/tree/master/example).