docs: document unit, integration, and installation (#4)

unit-test/README.md

@@ -0,0 +1,36 @@
+# Deploy Angular Universal to Vercel GitHub Actions
+
+A Github Action that runs the Unit Tests of a Magento Package
+
+## Inputs
+
+See the [action.yml](./action.yml)
+
+## Usage
+
+```yml
+name: Unit Test
+
+on:
+  push:
+    branches:
+    - main
+  pull_request:
+    branches:
+    - main
+
+jobs:
+  unit-test:
+    strategy:
+      matrix:
+        php_version:
+          - 7.4
+          - 8.1
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: graycoreio/github-actions-magento2/unit-test@main
+      with:
+        php_version: ${{ matrix.php_version }}
+        composer_auth: ${{ secrets.COMPOSER_AUTH }}
+```