Some bundlers don't support WebAssembly yet.
For example, Vite doesn't include the wasm file at all and returns a 404 HTML file instead, which returns in `CompileError: WebAssembly.instantiate(): expected magic word 00 61 73 6d, found 3c 21 44 4f @+0`. This is because Vite's HTML files start with `<!DOCTYPE html>`, and `3c 21 44 4f` is `<!DO`.
The fix is to allow users to specify a custom URL/module in `initWasm`, and they can then let the bundler handle it via `import ecashLibWasmUrl from 'ecash-lib/dist/ffi/ecash_lib_wasm_bg_browser.wasm?url'`.
wasm-bindgen doesn't provide the same for NodeJS, so we add a dummy param for typechecking.