Update RELEASE.md for R2-7-7

Author: LeandroMartinsdS

RELEASE.md

@@ -16,6 +16,10 @@ site location of dependencies.
 Release Notes
 =============
 
+R2-7-7 (Oct 2, 2025)
+* Extend SSH buffer length                              - PR [#142](https://github.com/DiamondLightSource/pmac/pull/142)
+* Update PowerPMAC trajectory to user shared-memory     - PR [#130](https://github.com/DiamondLightSource/pmac/pull/130)
+
 R2-7-4 (Sep 19, 2025)
 * Add EQU to ppmac trajectory scan code (#146)  - PR [#146](https://github.com/DiamondLightSource/pmac/pull/146)