Update README.md

Author: ef4

README.md

@@ -3,6 +3,13 @@ Ember-load-initializers
 
 A tiny library to autoload your initializer and instance initializer files in an Ember app. 
 
+Version 3.0.0 requires:
+
+ - ember-source >= 5
+ - ember-auto-import >= 2 or embroider
+
+Use 2.x for ember-source < 5 and classic ember-cli builds that lack ember-auto-import 2.
+
 License
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