docs: add codspeed link to readme

README.md

@@ -22,6 +22,8 @@
     <img alt="docs.rs" src="https://img.shields.io/docsrs/ganesh?style=for-the-badge&logo=rust&logoColor=red"></a>
   <a href="https://app.codecov.io/github/denehoffman/ganesh/tree/main/" alt="Codecov coverage report">
     <img alt="Codecov" src="https://img.shields.io/codecov/c/github/denehoffman/ganesh?style=for-the-badge&logo=codecov"></a>
+  <a href="https://codspeed.io/denehoffman/ganesh">
+    <img src="https://img.shields.io/endpoint?url=https%3A%2F%2Fcodspeed.io%2Fbadge.json&style=for-the-badge" alt="CodSpeed"/></a>
 </p>
 
 `ganesh` (/ɡəˈneɪʃ/), named after the Hindu god of wisdom, provides several common minimization algorithms as well as a straightforward, trait-based interface to create your own extensions. This crate is intended to be as simple as possible. The user needs to implement the `Function` trait on some struct which will take a vector of parameters and return a single-valued `Result` ($`f(\mathbb{R}^n) \to \mathbb{R}`$). Users can optionally provide a gradient function to speed up some algorithms, but a default central finite-difference implementation is provided so that all algorithms will work out of the box.