doc: added nice badges to inform on the project

Author: patrickjahns

README.md

@@ -1 +1,8 @@
-# openvpn_exporter
+# openvpn_exporter
+
+[![Release](https://img.shields.io/github/v/release/patrickjahns/openvpn_exporter?sort=semver)](https://github.com/patrickjahns/openvpn_exporter/releases)
+[![LICENSE](https://img.shields.io/github/license/patrickjahns/openvpn_exporter)](https://github.com/patrickjahns/openvpn_exporter/blob/master/LICENSE)
+[![Test and Build](https://github.com/patrickjahns/openvpn_exporter/workflows/Test%20and%20Build/badge.svg)](https://github.com/patrickjahns/openvpn_exporter/actions?query=workflow%3A%22Test+and+Build%22)
+[![Go Doc](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white)](https://pkg.go.dev/github.com/patrickjahns/openvpn_exporter)
+[![Go Report Card](https://goreportcard.com/badge/github.com/patrickjahns/openvpn_exporter)](https://goreportcard.com/report/github.com/patrickjahns/openvpn_exporter)
+