Migrate to flat config (#35)

Co-authored-by: Sindre Sorhus <[email protected]>

Author: TaishiKobari

.github/workflows/main.yml

@@ -10,12 +10,12 @@ jobs:
       fail-fast: false
       matrix:
         node-version:
-          - 16
-          - 14
-          - 12
+          - 22
+          - 20
+          - 18
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-node@v2
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
       - run: npm install