Add note to bump ext/libyuv version up to chrome
diff --git a/ext/libyuv.cmd b/ext/libyuv.cmd
index c30e9ca..907eeba 100755
--- a/ext/libyuv.cmd
+++ b/ext/libyuv.cmd
@@ -14,6 +14,9 @@
git clone --single-branch https://chromium.googlesource.com/libyuv/libyuv
cd libyuv
+: # When changing the commit below to a newer version of libyuv, it is best to make sure it is being used by chromium,
+: # because the test suite of chromium provides additional test coverage of libyuv.
+: # It can be looked up at https://source.chromium.org/chromium/chromium/src/+/main:DEPS?q=libyuv.
git checkout 4a3c79cb
mkdir build
