Allow Fallback DNS Options

It would be nice to have somewhere we can specify fallback DNS.

For example, if I want to use my browser for Work and General internet usage, I want everything not found by NextDNS to then try my specified fallback.

To enhance this even further, it would be nice to specify certain domains that would always use the fallback.

So far only Firefox is the only browser that does this in browser, all Chromium browsers and Safari do not have the option to allow "fallback" which then brakes certain internal sites (my VPN is split tunnel).

It would also enable users to set the DNS in their network settings, instead of browser and allow fallback capabilities.

For this to work, the user would have to specify their fallback DNS (unlike the browser, which relies on OS settings).

Example of Firefox's fallback.