docs: release: Add release notes

Adds release notes for various recent changes

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>
diff --git a/docs/release-notes.d/boot-serial-echo.md b/docs/release-notes.d/boot-serial-echo.md
index 2667f73..6116f05 100644
--- a/docs/release-notes.d/boot-serial-echo.md
+++ b/docs/release-notes.d/boot-serial-echo.md
@@ -1 +1,4 @@
-- Boot serial: Add response to echo command if support is not enabled, previously the command would have been accepted but no response indicating that the command is not supported would have been sent.
+- Boot serial: Add response to echo command if support is not
+  enabled, previously the command would have been accepted but no
+  response indicating that the command is not supported would have
+  been sent.