[feat] How to reuse an existing webInterface?

### What did you do?

In my case, I built a monitor server which was integrated with pprof.

```go
var switcher bool
if err := driver.PProf(&driver.Options{
Flagset: &internal.GoFlags{
Profile: profilePath + profile,
Http: "127.0.0.1:" + strconv.Itoa(internal.ListenPort),
NoBrowser: true,
},
HTTPServer: func(args *driver.HTTPServerArgs) error {
if switcher {
return nil
}
for k, v := range args.Handlers {
http.Handle("/ui"+k, v)
}
switcher = true
return nil
},
}); err != nil {
panic(err)
return
}
```

However I haven't found options to reuse existing webInterface, thus the code wouldn't work.

### What did you expect to see?

I modified the source code in internal/driver/webui.go:

```go
var webI = new(webInterface)

func makeWebInterface(p *profile.Profile, opt *plugin.Options) *webInterface {
templates := template.New("templategroup")
addTemplates(templates)
report.AddSourceTemplates(templates)

webI.prof = p
webI.options = opt
webI.help = make(map[string]string)
webI.templates = templates

return webI
}
```

It makes sense, but apparently it is not a good idea.

### What did you see instead?

I hope this feature could be an option in main function, or anything similarly. Thank you.