doc: add readme

Author: dorianneto

README.md

@@ -0,0 +1,13 @@
+# 🎛️ Feature Flag for Go
+
+<div style="text-align: center">
+
+[![Go Report Card](https://goreportcard.com/badge/github.com/dorianneto/ff4go)](https://goreportcard.com/report/github.com/dorianneto/ff4go)
+![GitHub go.mod Go version](https://img.shields.io/github/go-mod/go-version/dorianneto/ff4go)
+![GitHub License](https://img.shields.io/github/license/dorianneto/ff4go)
+
+</div>
+
+> Thank you for using ff4go! Feel free to report any [issue of improvement](https://github.com/dorianneto/ff4go/issues) 🙏
+
+## Table of contents