Update README.md

Author: lemire

README.md

@@ -1,4 +1,5 @@
 # ada_fetchcontent
+[![Ubuntu 22.04](https://github.com/ada-url/ada_fetchcontent/actions/workflows/ubuntu.yml/badge.svg)](https://github.com/ada-url/ada_fetchcontent/actions/workflows/ubuntu.yml)
 
 Demonstrates how to use ada as a CMake dependency with 
 `FetchContent`.
@@ -7,4 +8,4 @@ Demonstrates how to use ada as a CMake dependency with
 cmake -B build
 cmake --build build
 ./build/repro
-```
+```