Document that project is dormant.

README

diff --git a/README b/README
index 49debe9..0f46ee9 100644
--- a/README
+++ b/README
@@ -1,3 +1,5 @@
+Apache log4php was moved to dormant status on December 14, 2020. No pull requests or issues will be reviewed or acted upon.
+
 Apache log4php is a versatile logging framework for PHP.
 
 Apache log4php is a project at the Apache Software Foundation (ASF).