Add mendel 5.3 changelog

Change-Id: I9df7bd39058ee73d140a3841cf2ddfe70a93f164

Releases.md

diff --git a/Releases.md b/Releases.md
index d2b6da3..3787bd6 100644
--- a/Releases.md
+++ b/Releases.md
@@ -6,6 +6,13 @@
 
 For system image downloads, see [coral.ai/software](https://coral.ai/software/).
 
+## 5.3 (eagle)
+
++   Updated to latest ML release
++   Fixed boot from SD cards
++   Fixed MDT compatibility with Python 3.9
++   Added backup apt sources
+
 
 ## 5.2 (eagle)