Add backward compatibility message in README.md

Author: arshadal55

README.md

@@ -75,3 +75,14 @@ vainfo: Supported profile and entrypoints
       VAProfileVP9Profile2            : VAEntrypointVLD
       ...
 ```
+
+
+# Backward Compatibility
+No code changes may be introduced that would regress support for any currently supported hardware.
+All contributions must ensure continued compatibility and functionality across all supported hardware platforms.
+Failure to maintain hardware compatibility may result in the rejection or reversion of the contribution.
+
+Any deliberate modifications or removal of hardware support will be transparently communicated in the release notes.
+
+API options are solely considered as a stable interface.
+Any debug parameters, environmental variables, and internal data structures, are not considered as an interface and may be changed or removed at any time.