chore: update vitest to v4 (#61)

Author: fvsch

.github/workflows/test.yml

@@ -11,8 +11,8 @@ jobs:
     runs-on: ubuntu-latest
     name: Check types
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/checkout@v5
+      - uses: actions/setup-node@v6
         with:
           node-version: 22
       - run: npm ci
@@ -21,11 +21,11 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [18, 22]
+        node: [20, 22]
     name: Run tests on Node ${{ matrix.node }}
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/checkout@v5
+      - uses: actions/setup-node@v6
         with:
           node-version: ${{ matrix.node }}
       - run: npm ci