Bump node environment to 15.x

It updates node version to 15.x to be able to use
`String.prototype.replaceAll()`

.github/workflows/deploy-desktop.yaml

@@ -22,7 +22,7 @@ jobs:
       - name: Setup node
         uses: actions/setup-node@v1
         with:
-          node-version: '14.x'
+          node-version: 15.x
       - name: Install dependencies
         run: npm ci
       - name: Run tests

.github/workflows/deploy-site.yaml

@@ -83,7 +83,7 @@ jobs:
         name: "App: Setup node"
         uses: actions/setup-node@v1
         with:
-          node-version: '14.x'
+          node-version: 15.x
       -
         name: "App: Install dependencies"
         run: npm ci

.github/workflows/quality-checks.yaml

@@ -20,7 +20,7 @@ jobs:
       - name: Setup node
         uses: actions/setup-node@v1
         with:
-          node-version: 14.x
+          node-version: 15.x
       - name: Install dependencies
         run: npm ci
       - name: Lint

.github/workflows/security-checks.yaml

@@ -18,7 +18,7 @@ jobs:
         name: Setup node
         uses: actions/setup-node@v1
         with:
-          node-version: 14.x
+          node-version: 15.x
       -
         name: NPM audit
-        run: npm audit
+        run: exit "$(npm audit)" # Since node 15.x, it does not fail with error if we don't explicitly exit

.github/workflows/test.yaml

@@ -21,7 +21,7 @@ jobs:
         name: Setup node
         uses: actions/setup-node@v1
         with:
-          node-version: '14.x'
+          node-version: 15.x
       -
         name: Install dependencies
         run: npm ci