Switch from yarn -> npm, custom action -> dependabot

.github/dependabot.yml

@@ -1,8 +1,29 @@
 version: 2
+
 updates:
   - package-ecosystem: github-actions
     directory: '/'
     schedule:
       interval: weekly
       time: '04:00'
       timezone: America/New_York
+
+  - package-ecosystem: npm
+    directory: '/'
+    versioning-strategy: increase
+    schedule:
+      interval: weekly
+      time: '04:00'
+      timezone: America/New_York
+    groups:
+      prod:
+        dependency-type:
+          - 'production'
+      dev:
+        dependency-type:
+          - 'development'
+    ignore:
+      - dependency-name: '@types/node'
+      - dependency-name: 'node-fetch'
+        versions:
+          - 3.x

.github/workflows/test-wpt.yml

@@ -51,7 +51,7 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version-file: .nvmrc
-          cache: yarn
+          cache: npm
       - uses: actions/setup-python@v5
         with:
           python-version: '3.x'
@@ -66,8 +66,8 @@ jobs:
 
       - name: Build polyfill
         run: |
-          yarn install --immutable
-          yarn build:wpt
+          npm install
+          npm run build:wpt
 
       - name: Setup WPT
         run: |
@@ -83,7 +83,7 @@ jobs:
           ./wpt serve --inject-script=${{ github.workspace }}/dist/css-anchor-positioning-wpt.umd.cjs &
           cd ..
           cp -r wpt-results/test-results .
-          yarn test:wpt
+          npm run test:wpt
 
       - name: Push to WPT results branch
         run: |

.github/workflows/test.yml

@@ -18,12 +18,12 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version-file: .nvmrc
-          cache: yarn
+          cache: npm
       - name: Install dependencies
         run: |
-          yarn install --immutable
+          npm install
           npx playwright install --with-deps
-      - run: yarn test:ci
+      - run: npm run test:ci
 
   lint:
     name: Lint
@@ -33,8 +33,8 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version-file: .nvmrc
-          cache: yarn
+          cache: npm
       - name: Lint
         run: |
-          yarn install --immutable
-          yarn lint:ci
+          npm install
+          npm run lint:ci

.nvmrc

@@ -1 +1 @@
-v16.17
+v20

CONTRIBUTING.md

@@ -16,27 +16,27 @@ Please follow the [OddBird Code of Conduct](https://www.oddbird.net/conduct/).
 ## Development
 
 - Clone the repository.
-- Install dependencies: `yarn install`.
-- Start dev server: `yarn serve`. Visit `localhost:3000`.
+- Install dependencies: `npm install`.
+- Start dev server: `npm run serve`. Visit `localhost:3000`.
 
 ## Code style
 
 JS code is formatted with prettier, and CSS is formatted with stylelint.
 
-- Lint: `yarn lint:ci`
-- Format & lint: `yarn lint`
+- Lint: `npm run lint:ci`
+- Format & lint: `npm run lint`
 
 We recommend setting up your IDE to automatically format code for you.
 
 ## Testing
 
 Unit tests and end-to-end tests are available in the `tests/` folder.
 
-- Run all tests: `yarn test`
-- Run unit tests: `yarn test:unit`
+- Run all tests: `npm run test`
+- Run unit tests: `npm run test:unit`
 - Run end-to-end tests:
   - Configure Playwright (this step is only required once or when the version of
     `@playwright/test` changes in package.json):
     `npx playwright install --with-deps`
-  - Run tests (Chromium only): `yarn test:e2e`
-  - Run tests (Chromium, Firefox & Webkit): `yarn test:e2e:ci`
+  - Run tests (Chromium only): `npm run test:e2e`
+  - Run tests (Chromium, Firefox & Webkit): `npm run test:e2e:ci`