docs: use GitHub markdown for version notice (#46) [skip ci]

Author: twangodev

README.md

@@ -9,15 +9,15 @@
 The official Python library for the Fish Audio API
 
 **Documentation:** [Python SDK Guide](https://docs.fish.audio/developer-guide/sdk-guide/python/) | [API Reference](https://docs.fish.audio/api-reference/sdk/python/)
-
-> ### Important: Changes to PyPI Versioning
-> 
+> [!IMPORTANT]
+> ## Changes to PyPI Versioning
+>
 > For existing users on Fish Audio Python SDK, please note that the starting version is now `1.0.0`. The last version before this was `2025.6.3`. You may need to adjust your version constraints accordingly.
-> 
+>
 > The original API in the `fish_audio_sdk` package has NOT been removed, but you will not receive any updates if you continue using the old versioning scheme.
-> 
+>
 > The simplest fix is to update your dependency to `fish-audio-sdk>=1.0.0` to continue receiving updates, or by pinning to a specific version like `fish-audio-sdk==1.0.0` when installing via your package manager. There are no changes to the API itself in this transition.
-> 
+>
 > If you're using the legacy `fish_audio_sdk` and would like to switch to the newer, more robust `fishaudio` package, see the [migration guide](https://docs.fish.audio/archive/python-sdk-legacy/migration-guide) to upgrade.
 
 ## Installation