ci: add coverage

.github/workflows/coverage.yml

@@ -0,0 +1,17 @@
+name: Measure test coverage
+on:
+  - push
+  - pull_request
+jobs:
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@1e31de5234b9f8995739874a8ce0492dc87873e2 # v4
+      - uses: actions/setup-node@8f152de45cc393bb48ce5d89d36b731f54556e65 # v4
+        with:
+          node-version: 22
+          registry-url: 'https://registry.npmjs.org'
+          cache: npm
+      - run: npm install
+      - run: npm run build --if-present
+      - run: npm run test:coverage

package.json

@@ -20,7 +20,7 @@
     "lint": "prettier --check 'src/**/*.{js,ts}' 'test/**/*.{js,ts,mjs}'",
     "format": "prettier --write 'src/**/*.{js,ts}' 'test/**/*.{js,ts,mjs}'",
     "test": "node test/index.js",
-    "coverage": "c8 node test/index.js"
+    "test:coverage": "c8 node test/index.js"
   },
   "author": "Paul Miller (https://paulmillr.com)",
   "homepage": "https://paulmillr.com/noble/",