[PATCH] README: add GNU Project notice

[Eric Blake]

* README: Add section to attract more people towards the GNU project.
Inspired by a suggestion from Jose E. Marchesi <jemarch@gnu.org> on
the gnu-prog-discuss mailing list.
---
 README | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/README b/README
index 243d4779..d328a8a6 100644
--- a/README
+++ b/README
@@ -64,10 +64,29 @@ solution, from which the problem might be uneasy to infer.
 For any copyright year range specified as YYYY-ZZZZ in this package
 note that the range specifies every single year in that closed interval.

+GNU Project notice
+==================
+GNU M4 is part of the GNU Operating System, developed by the GNU Project.
+
+If you are the author of an awesome program and want to join us in
+writing Free (libre) Software, please consider making it an official
+GNU program and become a GNU Maintainer.  Instructions on how to do
+this are here:
+  https://www.gnu.org/help/evaluation
+
+Don't have a program to contribute?  Look at all the other ways to help:
+  https://www.gnu.org/help/help.html
+
+And to learn more about Free (libre) Software in general, please read
+and share this page:
+  https://gnu.org/philosophy/free-sw.html
+
+We are looking forward to hacking with you!
+
 ========================================================================

-Copyright (C) 2000, 2005-2014, 2016-2017, 2020 Free Software Foundation,
-Inc.
+Copyright (C) 2000, 2005-2014, 2016-2017, 2020-2021 Free Software
+Foundation, Inc.

 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
-- 
2.31.1