[Feature Request] Improve Metadata Explorer

[Radha]

https://wiki.polkadot.network/docs/metadata

• it would be cool, to have possibility select "custom endpoint", lets say I am running some local node (ws://localhost:1234) and want to browse metadata - something like polkadot.js.org/apps does
• it would be nice if AccountNonce could be displayed in snake case: account_nonce as this is how it has to be typed when used as a parameter to the rpc State Call 'method' parameter.

[Keith Alfaro]

I added some thoughts on the second point in #4517. For the first point, selecting a new dropdown option Custom Endpoint could reveal an addition input field below that would allow the user to enter a custom RPC source. This would probably take a bit of effort to ensure entering various types of malformed inputs doesn't cause crashes or other issues. Maybe something like a button next to the field that needs to be clicked which is responsible for validating the path and triggering the document update.