Add a project changelog

README.md

@@ -60,7 +60,9 @@ on that line.
 
 ## Version compatibility
 
-Gauges requires Minetest 5.0.0 or newer to work as expected.
+Gauges is currently primarily tested with Minetest 5.1.0. It may or may not work
+with newer or older versions. Issues arising in versions older than 5.0.0
+will generally not be fixed.
 
 ## License