Make ackee loadable from subfolder/same host

Hi there, i really like ackee for its clear visuals and simplicity. Also i can easily set it up with docker and reverse proxy.

**🐣 Is your feature request related to a problem? Please describe.**

If i understand correctly, ackee can only be loaded from a different (sub)domain. For this to work, you need to setup headers etc. Also you need to open another https connection with handshake etc. which can be slowish. This is not a real problem because ackee.js loads asynchronous.

**💡 Describe the solution you'd like**

Configure ackee to be loadable from a subfolder. This is already doable e.g.

- Main site hosted on `example.com`
- ackee-docker reverse proxied on `ackee.example.com`
- configure webserver to internally proxy `example.com/ackee.js` and `example.com/api` to same ackee-docker host as `ackee.example.com`.
- embed script but change source from `ackee.example.com/ackee.js` to `example.com/ackee.js`
- script is loaded and ackee counts visits on different hosts, but no second https connection is opened so site loads faster. Also i did not explicitly set up (cors-)headers for this and it still worked (with [caddy http server](https://caddyserver.com))
- ackee dashboard still reachable under `ackee.example.com`

I'm unsure if this breaks anything, because i couldn't find this setup in the docs. For me it is working.

**📋 Additional context**

This is surely more "nice to have" than a serious issue. Also maybe all of this already is implemented but i did not find it in the docs? Then please dismiss this request.

Greetings!