Hard-wired URLs in the source code

[dboreham]

There are a few places in the code where the deployment URL (e.g. https://scan.openlibra.io) is present in the code.
Problematic in terms of coupling the deployment of one instance of the code into code that should be deployable anywhere.

Cases:

OpenGraph metadata tags:
https://github.com/0LNetworkCommunity/explorer/blob/main/web-app/index.html#L21
The OG people messed this up -- it's not possible to use a relative URL here so we need
to find a way to inject the deployed URL at either deploy time or run time.

Non-configurable config:
https://github.com/0LNetworkCommunity/explorer/blob/main/web-app/src/config.ts#L19

and:
https://github.com/0LNetworkCommunity/explorer/blob/main/web-app/src/modules/aptos/Provider.tsx#L7

These seems simple enough to inject from an environment variable.

[dboreham]

We already have RPC_PROVIDER_URL in the api service environment.