Add "experimental" badge

README.md

@@ -1,3 +1,5 @@
+![stability: experimental](https://img.shields.io/badge/stability-experimental-red.svg)
+
 # Adnot
 
 **WARNING**: this repo contains unrepentant bikeshedding and wheel-reinvention. You almost definitely shouldn't use it, and it's probably best to disregard the entire thing!