add file name support for encryptFile & decryptFile

also adds supporting methods l/e int32 byteArray2int & int2byteArray
creates TextEncoder, TextDecoder objects in global module scope
creates magic value METADATA_LENGTH of 1020 + 4 (4 bytes * 255 chars, 4
bytes for int32)

webpack.config.js

@@ -7,7 +7,7 @@ module.exports = {
     path: path.resolve(__dirname, "dist"),
   },
   experiments: {
-    asyncWebAssembly: true,
+    syncWebAssembly: true,
   },
   mode: "development",
 };