Update CHANGELOG for libaom v3.4.0 (continued)

Add updates from Paul and Yunqing.

Bug: aomedia:3281
Change-Id: I7d567d82d86e13170d1240d964bd9c384c95a8bf

CHANGELOG

diff --git a/CHANGELOG b/CHANGELOG
index 3179441..4861a9c 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,4 +1,4 @@
-2022-06-14 v3.4.0
+2022-06-16 v3.4.0
   This release includes compression efficiency and perceptual quality
   improvements, speedup and memory optimizations, and some new features.
   There are no ABI or API breaking changes in this release.
@@ -47,10 +47,14 @@
 
   - Perceptual Quality Improvements
     * RTC: Visual quality improvements for high speeds (9/10)
+    * Improvements in coding quality for all intra mode
 
   - Speedup and Memory Optimizations
+    * ~10% speedup in good quality mode encoding.
     * Ongoing improvements to intra-frame encoding performance on Arm
     * Faster encoding speed for "--deltaq-mode=3" mode.
+    * Improved encoding speed for real time mode speeds 5 and 6 with
+      default settings
 
   - Bug Fixes
     * b/204460717: README.md: replace master with main