Automate via workflows. Add auto-archiving for downgrade. (#581)

.github/workflows/ci.yml

@@ -0,0 +1,32 @@
+name: CI
+on:
+    pull_request:
+        types: [opened, synchronize]
+        branches: [main]
+        paths: ['src/**', 'tests/**']
+    workflow_dispatch:
+
+jobs:
+    ci:
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@v4
+            - uses: pnpm/action-setup@v4
+              with:
+                  version: 9
+            - uses: actions/setup-node@v4
+              with:
+                  node-version: 20
+                  registry-url: https://registry.npmjs.org/
+                  cache: pnpm
+            - name: Install dependencies
+              run: pnpm i --frozen-lockfile
+            - name: Build
+              run: pnpm run build
+            - name: Lint
+              run: |
+                  pnpm run format:check
+                  pnpm run eslint
+            - name: Test
+              # NOTE: see jest.config.ts `collectCoverageFrom`
+              run: pnpm run coverage