Validate event on the Java daemon

[KoalaSat]

Right now the validation of incoming event occurs in JS, but this makes the process slower, would be great to implement the validation of signatures with Java, when the event is validated https://github.com/KoalaSat/nostros/blob/main/android/app/src/main/java/com/nostros/classes/Event.java#L59

I tried importing some libraries with no great success