Readme.txt is now in the correct folder.
But there are some possible issues. I took screenshots of those that are in the attachments.
1.) While importing the created package, there seems to be more in it than needed. I only dragged "GameJamTestFolder" to the exporter, but there are also my other testing folders shown (not selected though).
2.) If I press the delete/x-button after added asset it will throw an error in the console. It still works, but to let you know.
ArgumentOutOfRangeException: Argument is out of range.
Parameter name: index
System.Collections.Generic.List`1[System.String].get_Item (Int32 index) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Collections.Generic/List.cs:633)
PlaymakerGjamExporter._ShowThirdPartyAssets () (at Assets/PmGameJam/Editor/PlaymakerGjamExporter.cs:284)
PlaymakerGjamExporter.OnGUI () (at Assets/PmGameJam/Editor/PlaymakerGjamExporter.cs:85)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:232)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115)
UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at /Users/builduser/buildslave/unity/build/Editor/Mono/HostView.cs:295)
UnityEditor.HostView.Invoke (System.String methodName) (at /Users/builduser/buildslave/unity/build/Editor/Mono/HostView.cs:288)
UnityEditor.HostView.OldOnGUI () (at /Users/builduser/buildslave/unity/build/Editor/Mono/HostView.cs:107)
UnityEngine.Experimental.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt) (at /Users/builduser/buildslave/unity/build/Runtime/UIElements/Managed/IMGUIContainer.cs:182)