Add support to ENS's getContentHash for skylinks

[dghelm]

Describe the Feature

The ENS protocol and official frontend support setting a content hash for sia:// URIs, which are used to resolve content on the Skynet decentralized storage network.

The ETH,LIMO team requested this integration while building support for Skynet into their resolver. Loading webapps hosted on Skynet via ENS is already supported by Metamask's browser extension and Cloudflare's eth.link, and we'd love to see further adoption of decentralized storage standards.

The Skynet Labs team would be happy to make a PR, as we have experience dealing with the multi-codec and skylink formats.

Code Example

// for skynet-ens.eth

await resolver.getContentHash();
// 'sia://AQCRuTdTPzCyyU6I82eV7VDFVLPW82LJS9mH-chmjDlKUQ'

[ricmoo]

This is now available in 5.6.7. Try it out and let me know if you have any problems. :)