Add basic angle mask suggestions

Mask suggestions are a bit broken in general so this doesn't change much

worldedit-core/src/main/java/com/sk89q/worldedit/extension/factory/parser/mask/AngleMaskParser.java

@@ -18,6 +18,9 @@ public class AngleMaskParser extends RichParser<Mask> {
 
     @Override
     protected Stream<String> getSuggestions(String argumentInput, int index) {
+        if (index == 0 || index == 1) {
+            return suggestPositiveDoubles(argumentInput).flatMap(s -> Stream.of(s, s + "d"));
+        }
         return null;
     }