Upgrade to Node 15

Author: ehmicky

.github/workflows/workflow.yml

@@ -11,7 +11,7 @@ jobs:
       # We do not run each possible combination to make CI faster.
       matrix:
         os: [ubuntu-latest, macOS-latest, windows-latest]
-        node: [14]
+        node: [15]
         include:
           - os: ubuntu-latest
             node: 10.17.0
@@ -45,10 +45,10 @@ jobs:
     steps:
       - name: Git checkout
         uses: actions/checkout@v2
-      - name: Node.js 14
+      - name: Node.js 15
         uses: actions/setup-node@v1
         with:
-          node-version: 14
+          node-version: 15
       - name: Install dependencies
         run: npm ci
       # Test coverage check must happen after tests for the whole matrix have been