This is needed for support of WASM standard' https://www.w3.org/TR/wasm-web-api-1/#streaming-modules instantiateStreaming and compileStreaming,
and causes errors like
```
WASM: wasm streaming compile failed: TypeError: Failed to execute 'compile' on 'WebAssembly': Incorrect response MIME type. Expected 'application/wasm'.
```
since plain text is returned instead.
It also doesn't seem to be easily fixable even with `nginx.conf.sigil` substitution
This allows folks the ability to restore the previous routing functionality used by static sites backed by VueJS (as an example).
Note that all requests routed this way will respond with a '200 OK' on the server, potentially causing SEO issues.
Closes#53
Prior to this, I was seeing the successful HTTP status 200 when
requesting files that did not exist.
With this change, the server sends back Nginx's default 404 page instead
of the home page.
