.github/workflows: update NodeJS to 20

With all dependency upgrade I've done, the support for NodeJS 12 is now
broken. So it's time to move on to a newer, still supported version.

NodeJS 20 is choosen because a.) while it's not an LTS yet, it will
become an LTS soon, and b.) it matches the version in netdev/devenv
Docker image.

Author: peat-psuwit

.github/workflows/npm-test.yml

@@ -14,9 +14,11 @@ jobs:
       - name: Prepare Node.js
         uses: actions/setup-node@v1
         with:
-          node-version: '12.x'
-      - name: Run `npm install`
-        run: npm install
+          node-version: '20.x'
+      - name: Run `npm ci`
+        # See the PR below for why `--legacy-peer-deps`` is needed.
+        # https://github.com/netdata/dashboard/pull/467
+        run: npm ci --legacy-peer-deps
       - name: Run `npm test`
         run: npm test
   npm-lint:
@@ -28,8 +30,8 @@ jobs:
       - name: Prepare Node.js
         uses: actions/setup-node@v1
         with:
-          node-version: '12.x'
-      - name: Run `npm install`
-        run: npm install
+          node-version: '20.x'
+      - name: Run `npm ci`
+        run: npm ci --legacy-peer-deps
       - name: Run `npm run lint`
         run: npm run lint

.github/workflows/release.yml

@@ -17,9 +17,11 @@ jobs:
       - name: 'Prepare Node.js'
         uses: actions/setup-node@v1
         with:
-          node-version: '12.x'
-      - name: 'Fetch Dependencies'
-        run: npm install
+          node-version: '20.x'
+      - name: Run `npm ci`
+        # See the PR below for why `--legacy-peer-deps`` is needed.
+        # https://github.com/netdata/dashboard/pull/467
+        run: npm ci --legacy-peer-deps
       - name: 'Build Dashboard'
         run: npm run build
       - name: 'Prepare Tarball'