Support /dns-query for DoH from Autoconf

[lidel]

#123 introduced support for autoconf, and it provides optional DNS resolvers, such as one for .eth.

With very little effort Someguy could

• expose /dns-query endpoint for DoH that acts as a caching proxy for Autoconf config
• have configuration option for overriding autoconf "auto" placeholders, similar how Kubo does it

This way people could use Someguy as one-stop-shop for IPFS and DNS routing needs, similar to what we already do at delegated-ipfs.dev with some extra proprietary Nginx glue.