doc: 3.2.0-preview1 post release

Added 3.2.0-preview1 doc edits.

Signed-off-by: Francesco Domenico Servidio <[email protected]>

Author: FrancescoSer

doc/nrf/releases_and_maturity/release_notes.rst

@@ -21,6 +21,7 @@ This page is included only in the latest documentation, because it might contain
    :caption: Subpages:
 
    releases/release-notes-changelog
+   releases/release-notes-3.2.0-preview1
    releases/release-notes-3.1.1
    releases/release-notes-3.1.0
    releases/release-notes-3.1.0-preview3