CI: test Node.js 15.

.github/workflows/browserstack.yml

@@ -5,7 +5,7 @@ on:
 
 env:
   FORCE_COLOR: 2
-  NODE: 14.x
+  NODE: 15.x
 
 jobs:
   browserstack:

.github/workflows/bundlewatch.yml

@@ -8,7 +8,7 @@ on:
 
 env:
   FORCE_COLOR: 2
-  NODE: 14.x
+  NODE: 15.x
 
 jobs:
   bundlewatch:

.github/workflows/css.yml

@@ -8,7 +8,7 @@ on:
 
 env:
   FORCE_COLOR: 2
-  NODE: 14.x
+  NODE: 15.x
 
 jobs:
   css:

.github/workflows/docs.yml

@@ -8,7 +8,7 @@ on:
 
 env:
   FORCE_COLOR: 2
-  NODE: 14.x
+  NODE: 15.x
 
 jobs:
   docs:

.github/workflows/js.yml

@@ -17,7 +17,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node: [10, 12, 14]
+        node: [10, 12, 14, 15]
 
     steps:
       - name: Clone repository

.github/workflows/lint.yml

@@ -8,7 +8,7 @@ on:
 
 env:
   FORCE_COLOR: 2
-  NODE: 14.x
+  NODE: 15.x
 
 jobs:
   lint:

.github/workflows/node-sass.yml

@@ -8,7 +8,7 @@ on:
 
 env:
   FORCE_COLOR: 2
-  NODE: 14.x
+  NODE: 15.x
 
 jobs:
   css: