docs: add DD shield

Author: MilesCranmer

README.md

@@ -4,7 +4,7 @@
 
 *Ridiculously fast dynamic expressions.*
 
-[![](https://img.shields.io/badge/docs-dev-blue.svg)](https://symbolicml.org/DynamicExpressions.jl/dev) [![CI](https://github.com/SymbolicML/DynamicExpressions.jl/actions/workflows/CI.yml/badge.svg)](https://github.com/SymbolicML/DynamicExpressions.jl/actions/workflows/CI.yml) [![Coverage Status](https://coveralls.io/repos/github/SymbolicML/DynamicExpressions.jl/badge.svg?branch=master)](https://coveralls.io/github/SymbolicML/DynamicExpressions.jl?branch=master) [![Aqua QA](https://raw.githubusercontent.com/JuliaTesting/Aqua.jl/master/badge.svg)](https://github.com/JuliaTesting/Aqua.jl)
+[![](https://img.shields.io/badge/docs-dev-blue.svg)](https://symbolicml.org/DynamicExpressions.jl/dev) [![CI](https://github.com/SymbolicML/DynamicExpressions.jl/actions/workflows/CI.yml/badge.svg)](https://github.com/SymbolicML/DynamicExpressions.jl/actions/workflows/CI.yml) [![Coverage Status](https://coveralls.io/repos/github/SymbolicML/DynamicExpressions.jl/badge.svg?branch=master)](https://coveralls.io/github/SymbolicML/DynamicExpressions.jl?branch=master) [![Aqua QA](https://raw.githubusercontent.com/JuliaTesting/Aqua.jl/master/badge.svg)](https://github.com/JuliaTesting/Aqua.jl) [![DispatchDoctor](https://img.shields.io/badge/%F0%9F%A9%BA_tested_with-DispatchDoctor.jl-blue?labelColor=white)](https://github.com/MilesCranmer/DispatchDoctor.jl)
 
 DynamicExpressions.jl is the backbone of [SymbolicRegression.jl](https://github.com/MilesCranmer/SymbolicRegression.jl) and
 [PySR](https://github.com/MilesCranmer/PySR).