add filter-exports command to automatically remove unused exports

this removes the need for a manual step in the rust example

uw8-tool/src/lib.rs

@@ -1,5 +1,7 @@
 mod base_module;
 mod pack;
+mod filter_exports;
 
 pub use base_module::BaseModule;
 pub use pack::{pack, pack_file, unpack, unpack_file, PackConfig};
+pub use filter_exports::filter_exports;