Add Readme with example usage.

README.md

@@ -0,0 +1,28 @@
+# WoW Lua Lint
+
+This action will lint all lua files specified for a given repository and check for any syntax issues (under the hood it uses `luac -p path/to/files`)
+
+## Usage
+
+The following shows an example of how to use this action in a workflow.
+
+.github/workflows/lint.yml
+
+```yaml
+name: Lint
+on: [push]
+
+jobs:
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout
+        uses: actions/checkout@v2
+        with:
+          repository: 'ps-wow/action-test-repo'
+      - name: wow-lint
+        uses: davidcraig/[email protected]
+        with:
+            path-to-files: 'src/test.lua'
+```