docs(readme): set width instead of height for table images, center the table

Author: EchoEllet

README.md

@@ -16,9 +16,13 @@ which uses [`file_selector`](https://pub.dev/packages/file_selector).
 > [!NOTE]
 > This native picker depends on the photos in the [Photos for MacOS App](https://www.apple.com/in/macos/photos/), which uses the [Apple PhotosUI](https://developer.apple.com/documentation/photosui) Picker, also known as PHPicker.
 
+<center>
+
 | Default picker | Native picker |
 |-------------------|-------------------|
-| <img src="https://github.com/CompileKernel/native-image-picker-macos/blob/main/readme_assets/image-picker-macos-file-selector.png?raw=true" alt="Default picker" height="400"/> | <img src="https://github.com/CompileKernel/native-image-picker-macos/blob/main/readme_assets/native-image-picker-macos-phpicker.png?raw=true" alt="macOS PHPicker" height="400"/> |
+| <img src="https://github.com/CompileKernel/native-image-picker-macos/blob/main/readme_assets/image-picker-macos-file-selector.png?raw=true" alt="Default picker" width="300"/> | <img src="https://github.com/CompileKernel/native-image-picker-macos/blob/main/readme_assets/native-image-picker-macos-phpicker.png?raw=true" alt="macOS PHPicker" width="300"/> |
+
+</center>
 
 ## ✨ Features