feat: detect typescript enable on env.VITEST === 'true'

Author: fengmk2

src/import.ts

@@ -36,8 +36,9 @@ let _supportTypeScript: boolean | undefined;
 export function isSupportTypeScript() {
   if (_supportTypeScript === undefined) {
     const extensions = getRequire().extensions;
-    _supportTypeScript = extensions['.ts'] !== undefined;
-    debug('[isSupportTypeScript] %o, extensions: %j', _supportTypeScript, Object.keys(extensions));
+    _supportTypeScript = extensions['.ts'] !== undefined || process.env.VITEST === 'true';
+    debug('[isSupportTypeScript] %o, extensions: %j, process.env.VITEST: %j',
+      _supportTypeScript, Object.keys(extensions), process.env.VITEST);
   }
   return _supportTypeScript;
 }