Sorting properties files

[Vlatombe]

Properties files are often subject to scm merge conflicts.

It would be nice for spotless to have the ability to sort them alphabetically.

[jglick]

https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/Properties.html to be clear. https://github.com/apache/netbeans/blob/dbb80507449c2ea148150d013f13d95cce810319/platform/openide.util/src/org/openide/util/EditableProperties.java may be useful.