docs: Add example

Author: LukeSavefrogs

README.md

@@ -1,2 +1,21 @@
 # setup-jython
-Github action that downloads and installs Jython
+
+[![Jython tests](https://github.com/LukeSavefrogs/setup-jython/actions/workflows/test-action.yml/badge.svg)](https://github.com/LukeSavefrogs/setup-jython/actions/workflows/test-action.yml)
+
+This action provides the following functionality for GitHub Actions users:
+
+- Installing a version of Jython and adding it to `PATH`
+
+## Basic usage
+
+```yml
+steps:
+- uses: actions/checkout@v3
+
+- name: Install Jython
+  uses: actions/setup-jython@v1
+  with:
+    jython-version: '2.5.2'
+
+- run: jython -c 'import sys, os; print(os.name, sys.version)';
+```