Add interactive REST API playground to ENSAdmin

[lightwalker-eth]

@notrab What do you think about updating the ENSAdmin nav bar here so that it would add each of the categories of REST APIs that ENSApi publishes via its openapi.json?

It would be pretty cool if we dynamically generated an interactive REST API docs playground for each category of REST APIs here in the ENSAdmin nav bar.

Key goals include:

1. Creating visibility of all the APIs published by an ENSApi instance (not only the GraphQL APIs (Omnigraph and Subgraph)).
2. You're already adding an interactive REST API docs playground into the ENSNode docs site. This is fantastic and will be the "default" place that people discover our REST APIs. It can always work off of the main production ENSNode instance at api.alpha.ensnode.io. However there's also a use case for having interactive REST API playgrounds for other ENSNode instances that are not the main production ENSNode instance. For example: for a Sepolia instance of ENSNode. This goal can be achieved via the mechanism described in this issue.

Special note:

1. Implementing this goal with a nice UX likely also requires us to stop making the "Services" list in the main nav menu static such that they are always visible no matter the state of the connection.
2. The vision for the ENSAdmin navigation menu has always been that it would be dynamically generated based on the state of the connection. In other words:
   1. If there's no active connection, there's no services to list.
   2. When an active connection is established, the services list would enter a loading state until it would be fully ready to render. During this loading state is when ENSAdmin might fetch and parse the openapi.json file from ENSApi such that it had all the knowledge needed for how to render the services navigation bar.
   3. Once all knowledge that's needed to render the services navigation bar has been fetched and parsed, the full services navigation bar can appear at the same time.

[notrab]

I eventually got this to work inside ENSAdmin. I'll tidy up some linting errors and get a branch pushed for you to peruse @lightwalker-eth 🚀