switch from Jest to Vitest

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

vitest.config.ts

@@ -0,0 +1,33 @@
+/**
+ * Copyright 2026 actions-toolkit authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {defineConfig} from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    clearMocks: true,
+    environment: 'node',
+    setupFiles: ['dotenv/config', './__tests__/.setup/setup.unit.ts'],
+    include: ['**/*.test.ts'],
+    coverage: {
+      all: true,
+      provider: 'v8',
+      reporter: ['clover'],
+      include: ['src/**/*.ts'],
+      exclude: ['src/**/index.ts', 'lib/**', 'node_modules/**', '__mocks__/**', '__tests__/**']
+    }
+  }
+});