Implement Clone for InvalidShutdownScript

Users hopefully shouldn't have much of a reason to use this, but
the bindings may need it to ensure no leaking pointers over an ffi.

Author: TheBlueMatt

lightning/src/ln/script.rs

@@ -21,7 +21,7 @@ use io;
 pub struct ShutdownScript(ShutdownScriptImpl);
 
 /// An error occurring when converting from [`Script`] to [`ShutdownScript`].
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct InvalidShutdownScript {
 	/// The script that did not meet the requirements from [BOLT #2].
 	///