Whole new world

Updated to use new libdeflate integration that I implemented upstream in https://github.com/shssoichiro/oxipng/pull/203.

codecs/oxipng/src/lib.rs

@@ -1,7 +1,10 @@
+mod malloc_shim;
+
 use wasm_bindgen::prelude::*;
 
 #[wasm_bindgen(catch)]
 pub fn optimise(data: &[u8], level: u8) -> Vec<u8> {
-  let options = oxipng::Options::from_preset(level);
+  let mut options = oxipng::Options::from_preset(level);
+  options.deflate = oxipng::Deflaters::Libdeflater;
   oxipng::optimize_from_memory(data, &options).unwrap_throw()
 }