⚒ update CI matrix

Author: mysticatea

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
       - name: Install Node.js
         uses: actions/setup-node@v1
         with:
@@ -25,24 +25,43 @@ jobs:
 
   test:
     name: Test
-    runs-on: ubuntu-latest
 
     strategy:
       matrix:
-        eslint: [6.x, 5.x, 4.x]
-        node: [12.x, 10.x, 8.x]
-        exclude:
-          # Run ESLint 5.x only on the latest Node.
-          - eslint: 5.x
+        eslint: [6.x]
+        node: [14.x]
+        os: [ubuntu-latest]
+        include:
+          # On other platforms
+          - eslint: 6.x
+            node: 14.x
+            os: windows-latest
+          - eslint: 6.x
+            node: 14.x
+            os: macos-latest
+          # On old Node.js versions
+          - eslint: 6.x
+            node: 12.x
+            os: ubuntu-latest
+          - eslint: 6.x
+            node: 10.x
+            os: ubuntu-latest
+          - eslint: 6.x
             node: 8.x
+            os: ubuntu-latest
+          # On old ESLint versions
           - eslint: 5.x
-            node: 10.x
-          # Run ESLint 4.x only on the latest Node.
+            node: 14.x
+            os: ubuntu-latest
           - eslint: 4.x
-            node: 8.x
+            node: 14.x
+            os: ubuntu-latest
+          # On the minimum supported ESLint/Node.js version
           - eslint: 4.x
-            node: 10.x
+            node: "8.0.0"
+            os: ubuntu-latest
 
+    runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout
         uses: actions/checkout@v1