gateway(encoding): support utf-8

[Arqu]

Very little care is given for properly handling or responding to utf-8 based urls or headers.

[b5]

can confirm this is a problem. Example: https://cloudflare-ipfs.com/ipfs/QmYwAPJzv5CZsnA625s3Xf2nemtYgPpHdWEz79ojWnPbdG/readme renders properly, on iroh, not so much:

[fabricedesre]

That's because cloudflare does content-type sniffing and returns content-type: text/plain; charset=utf-8 while the browser fails to figure out it's utf-8.

That's a dupe of #203