feat: get all available browsers?

[jinzhongjia]

It may not be enough to only get the best browser, because different browsers are slightly different, so return all browsers and let the developer decide which one is better?

[hassandraga]

return all browsers

I guess we can add this API to the core, then let wrappers loop trough all browsers and then create a native array of available browsers.

if (webui_browser_exist(Firefox)) {
    // ...
}

[hassandraga]

Implemented (d0b013c).