feat: set custom cache directory (#227)

kokoro.js/src/kokoro.js

@@ -150,6 +150,12 @@ export class KokoroTTS {
 }
 
 export const env = {
+  set cacheDir(value) {
+    hf.cacheDir = value
+  },
+  get cacheDir() {
+    return hf.cacheDir
+  },
   set wasmPaths(value) {
     hf.backends.onnx.wasm.wasmPaths = value;
   },