update docs link in README.md (#246)

Author: hyrodium

README.md

@@ -1,10 +1,10 @@
 # ReverseDiff
 
+[![Stable](https://img.shields.io/badge/docs-stable-blue.svg)](https://juliadiff.org/ReverseDiff.jl/stable)
+[![Dev](https://img.shields.io/badge/docs-dev-blue.svg)](https://juliadiff.org/ReverseDiff.jl/dev)
 [![Build status](https://github.com/JuliaDiff/ReverseDiff.jl/workflows/CI/badge.svg)](https://github.com/JuliaDiff/ReverseDiff.jl/actions)
 [![codecov.io](https://codecov.io/github/JuliaDiff/ReverseDiff.jl/coverage.svg?branch=master)](https://codecov.io/github/JuliaDiff/ReverseDiff.jl?branch=master)
 
-[**Go To ReverseDiff's Documentation**](https://juliadiff.org/ReverseDiff.jl/)
-
 [**See ReverseDiff Usage Examples**](https://github.com/JuliaDiff/ReverseDiff.jl/tree/master/examples)
 
 ReverseDiff is a fast and compile-able tape-based **reverse mode automatic differentiation (AD)** that