New websiteUrl field in Chain type

[leovct]

I'd like to be able to list some chains that my dApp supports and provide a link to the website/documentation of the chain. For example, the Ethereum chain would have a reference to https://ethereum.org/.

At the moment, I'm redirecting users to the default block explorer website but that's not really what I want. I think adding this little feature to @wagmi/chains would further enhance this already incredible package.

Happy to implement the change in a PR if you find it relevant!

edit: PR submitted #463