autoconf: maint: add outline for future NEWS

https://github.com/libsdl-org/autoconf/commit/697c1a07cd0bd0b03513d41f83762a5e9b742b2f

From 697c1a07cd0bd0b03513d41f83762a5e9b742b2f Mon Sep 17 00:00:00 2001
From: Zack Weinberg <[EMAIL REDACTED]>
Date: Tue, 8 Dec 2020 20:53:13 -0500
Subject: [PATCH] maint: add outline for future NEWS

---
 NEWS | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/NEWS b/NEWS
index 2a4db5f6..9006933b 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,10 @@ GNU Autoconf NEWS - User visible changes.
 
 * Noteworthy changes in release ?.? (????-??-??) [?]
 
+** Backward incompatibilities
+** New features
+** Obsolete features and new warnings
+** Notable bug fixes
 
 * Noteworthy changes in release 2.70 (2020-12-08) [stable]