Add workflow badge to README

Make it so I can see unit test status on the main page of the repo. :)

.github/workflows/test.yml

@@ -1,6 +1,6 @@
 # This starter workflow is for a CMake project running on a single platform. There is a different starter workflow if you need cross-platform coverage.
 # See: https://github.com/actions/starter-workflows/blob/main/ci/cmake-multi-platform.yml
-name: CMake on a single platform
+name: Unit Tests
 
 on:
   push:

README.md

@@ -1,5 +1,7 @@
 # libadagio-plusplus
 
+![Unit Test Status](https://github.com/meisekimiu/libadagio-plusplus/actions/workflows/test.yml/badge.svg)
+
 This is a WIP 2D game engine I'm working on. The main focus of this engine is to make it easy to switch between
 underlying libraries without changing any code besides some humble adapter classes.