Unix socket is expected to be encoded with `%2F`

## Describe the bug

**Node.js version:**
18.15.0

**OS version:**
Ubuntu 20.4

**Superagent version:**
8.0.9

**Description:**
As we can see from [line 728 of src/node/index.js](https://github.com/ladjs/superagent/blob/e7970e94504ea1358ecb0ea6f739e645644eb35a/src/node/index.js#L728) superagent expects a unix socket address like `/path/to/socket.sock` to be formatted as `%2Fpath%2Fto%2Fsocket.sock`, to then separate the socket path from the actual url with a regular expression.

If the unix path is not formatted as required, an unclear error will be thrown:
`Cannot read properties of null (reading '1') `
which is caused by the regexr not being able to match the unix socket path.

## Code to reproduce

```javascript
await superagent .get('http+unix:///path/to/socket.sock/the/actual/url');

// will throw: Cannot read properties of null (reading '1')

```

It would be much easier to just skip this whole pattern matching and provide and option to directly pass the socket path.
```javascript
await superagent.get('http://the/actual/url').socket('/path/to/socket.sock')

```
## Checklist

- [x] I have searched through GitHub issues for similar issues.
- [x] I have completely read through the README and documentation.
- [x] I have tested my code with the latest version of Node.js and this package and confirmed it is still not working.