feat: detect typescript enable on env.VITEST === 'true' (#42)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- Improved the logic for detecting TypeScript compatibility by
incorporating an additional environment condition.
- Introduced a new utility to streamline the retrieval of module
extension information for better consistency.

- **Tests**
- Updated the verification suite to include the newly exposed utility in
the module's public interface.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: fengmk2

src/import.ts

@@ -32,12 +32,17 @@ function getRequire() {
   return _customRequire;
 }
 
+export function getExtensions() {
+  return getRequire().extensions;
+}
+
 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));
+    const extensions = getExtensions();
+    _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;
 }

test/index.test.ts

@@ -38,6 +38,7 @@ describe('test/index.test.ts', () => {
         'default',
         'detectType',
         'getConfig',
+        'getExtensions',
         'getFrameworkOrEggPath',
         'getFrameworkPath',
         'getLoadUnits',