doc: release: 2.6: Add note about west bossac runner

Add release note about improvements in west bossac runner.

Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>
diff --git a/doc/releases/release-notes-2.6.rst b/doc/releases/release-notes-2.6.rst
index 75bd946..6a102cd 100644
--- a/doc/releases/release-notes-2.6.rst
+++ b/doc/releases/release-notes-2.6.rst
@@ -413,6 +413,13 @@
 
   - :c:macro:`DT_COMPAT_GET_ANY_STATUS_OKAY`: new macro
 
+* West
+
+  * Improve bossac runner.  Added legacy mode option into extended SAM-BA
+    bootloader selection.  This extends compatibility between Zephyr and
+    some Arduino IDE bootloaders.
+
+
 Libraries / Subsystems
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