docs: Update MongoDB driver README with QueryAST info

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

packages/drivers/mongo/README.md

@@ -2,6 +2,8 @@
 
 MongoDB driver for ObjectQL. Supports basic CRUD, filtering, and aggregation pipelines on MongoDB.
 
+**Now with ObjectStack QueryAST support!** This driver implements both the legacy `Driver` interface and the new `DriverInterface` from `@objectstack/spec` for seamless integration with the ObjectStack ecosystem.
+
 ## Installation
 
 ```bash
@@ -24,3 +26,59 @@ const objectql = new ObjectQL({
     }
 });
 ```
+
+## Features
+
+- ✅ **100% Backward Compatible** - All existing code continues to work
+- ✅ **QueryAST Support** - Supports the new `@objectstack/spec` query format
+- ✅ **Smart ID Mapping** - Automatic conversion between `id` (API) and `_id` (MongoDB)
+- ✅ **Full-Text Search** - MongoDB text search capabilities
+- ✅ **Array & JSON Fields** - Native BSON support for complex data types
+- ✅ **Aggregation Pipelines** - Native MongoDB aggregation support
+
+## Driver Metadata
+
+```typescript
+console.log(driver.name);     // 'MongoDriver'
+console.log(driver.version);  // '3.0.1'
+console.log(driver.supports); 
+// {
+//   transactions: true,
+//   joins: false,
+//   fullTextSearch: true,
+//   jsonFields: true,
+//   arrayFields: true
+// }
+```
+
+## QueryAST Format
+
+The driver now supports both legacy and QueryAST formats:
+
+### Legacy Format
+```typescript
+const results = await driver.find('users', {
+    filters: [['age', '>', 18]],
+    sort: [['name', 'asc']],
+    limit: 10,
+    skip: 0
+});
+```
+
+### QueryAST Format
+```typescript
+const results = await driver.find('users', {
+    filters: [['age', '>', 18]],
+    sort: [{ field: 'name', order: 'asc' }],
+    top: 10,  // Instead of 'limit'
+    skip: 0
+});
+```
+
+## Migration Guide
+
+See [MIGRATION.md](./MIGRATION.md) for detailed information about the ObjectStack migration and QueryAST format support.
+
+## License
+
+MIT