Add GH workflow

.github/workflows/checks.yaml

@@ -0,0 +1,19 @@
+env:
+  JWT_SIGNING_PUBLIC_KEY: ${{ secrets.JWT_SIGNING_PUBLIC_KEY }}
+  JWT_SIGNING_PRIVATE_KEY: ${{ secrets.JWT_SIGNING_PRIVATE_KEY }}
+on:
+  push:
+    branches:
+      - "main"
+  pull_request:
+    branches:
+      - "main"
+jobs:
+  tests:
+    runs-on: "ubuntu-latest"
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+      - run: "bundle exec rspec spec"