Add badges to README

[kristinapathak]

badges missing:

• maintainability
• code climate
• license
• release

should match this README:
https://github.com/xmidt-org/svalinn

[a18nov]

I have done license and release, but for maintainability and code climate I'd have to login in on Codeclimate.com

[kristinapathak]

I think I will need the help of @schmidtw to figure out how to add the remaining two.

[joe94]

@kristinaspring, saw that viper is using the new go.dev badge icon https://github.com/spf13/viper/blob/master/README.md

Here's the format

[![go.dev reference](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white&style=flat-square)](https://pkg.go.dev/mod/github.com/spf13/viper)