update readme with hw encode/decode options (#782)

Author: davidzhao

README.md

@@ -29,7 +29,9 @@ Use this SDK to add realtime video, audio and data features to your Rust app. By
 - [ ] Adaptive Streaming
 - [ ] Dynacast
 - [x] Hardware video enc/dec
-  - [x] VideoToolbox for MacOS/iOS
+  - [x] H.264, H.265 using VideoToolbox (MacOS/iOS)
+  - [x] H.264 on NVidia and AMD GPUs (Linux)
+  - [ ] H.264, H.265 on NVidia Jetson (Linux)
 - Supported Platforms
   - [x] Windows
   - [x] MacOS