UI for inspecting and customizing routing and trustless gateways

[lidel]

UX papercut identified by @aschmahmann while prototyping things against custom gateway.

Problem

There is no UI for inspecting or changing which gateways are used by IPLD Explorer.

Solution

There should be UI for adjusting gateways and delegated routing endpoints used by IPLD Explorer.

We have prior art in https://github.com/ipfs/service-worker-gateway: