🧪 [Tests] Install vitest and author suite (#20)

.changeset/lazy-months-grow.md

@@ -0,0 +1,5 @@
+---
+'emitten': minor
+---
+
+Author test suite and require tests to pass on PRs.

.github/workflows/test.yml

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+name: Test
+on: [push]
+
+jobs:
+  test:
+    name: Run test suites
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v3
+
+      - name: Setup Node 18.x to install with private scope
+        uses: actions/setup-node@v3
+        with:
+          node-version: 18
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Test
+        run: npm run test