ci: Check whether npm deduping is needed

.github/workflows/check-npm.yaml

@@ -0,0 +1,23 @@
+name: Check - npm and dependencies
+
+on:
+  pull_request:
+    paths:
+      - ".github/actions/npm-tools-setup/**"
+      - ".github/workflows/check-npm.yaml"
+      - "package.json"
+      - "package-lock.json"
+  workflow_call:
+  workflow_dispatch:
+
+jobs:
+  duplicate-dependencies:
+    name: Check for duplicate dependencies
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+      - name: Setup npm tools
+        uses: ./.github/actions/npm-tools-setup
+      - name: Check for duplicate dependencies
+        run: npm run check:npm:dedupe

package.json

@@ -1,6 +1,7 @@
 {
   "scripts": {
     "check:github-actions": "git ls-files '.github/**.yaml' | xargs -t -I {} action-validator {}",
+    "check:npm:dedupe": "npm find-dupes",
     "check:prettier": "prettier --check .",
     "check:renovateconfig": "npx --package=renovate -- renovate-config-validator --strict",
     "fix:prettier": "prettier --write ."

taskfile.yaml

@@ -10,6 +10,10 @@ tasks:
     desc: "Check - Github actions"
     cmds:
       - npm run check:github-actions
+  check:npm:dedupe:
+    desc: "Check - npm dedupe"
+    cmds:
+      - npm run check:npm:dedupe
   check:prettier:
     desc: "Check - prettier"
     cmds: