Add Best Practices badge to README

Signed-off-by: Matt Ray <github@mattray.dev>

README.md

@@ -1,3 +1,6 @@
+[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
+[![OpenSSF Best Practices](https://www.bestpractices.dev/projects/6219/badge)](https://www.bestpractices.dev/projects/6219)
+
 <img src="./opencost-header.png"/>
 
 # OpenCost — your favorite open source cost monitoring tool for Kubernetes and cloud spend