Alias event as report

This alias is made so people with OpenSMTPD filters knowledge will
directly understand that events are reports.

opensmtpd-derive/src/lib.rs

@@ -64,3 +64,8 @@ pub fn event(attr: TokenStream, input: TokenStream) -> TokenStream {
     };
     output.into()
 }
+
+#[proc_macro_attribute]
+pub fn report(attr: TokenStream, input: TokenStream) -> TokenStream {
+    event(attr, input)
+}