Update release notes

RELEASENOTES.md

@@ -2,7 +2,13 @@
 
 ### Latest dev branch (from r1.3.1) ###
 
-* TBC
+* DataSource improvements: DefaultUriDataSource now handles `file://`, `asset://`, `http://`,
+  `https://` and `content://` URIs automatically. It also handles `file:///android_asset/*` URIs,
+  and file paths like `/path/to/media.mp4` where the scheme is not specified (`file://` is assumed
+  in this case).
+* HLS: Fix for some ID3 events being dropped.
+* HLS: Correctly handle 0x0 and floating point RESOLUTION tags.
+* Mp3Extractor: robustness improvements.
 
 ### r1.3.1 ###