Add a constant variable for supported chain IDs

[manumonti]

The supported chains for the TACo conditions can vary over the time due to the deprecation of the different networks or because we decide to support only some testnets depending on the domain used (especially on Lynx, Tapir...).

We can add a constant variable to taco-web containing the chain ID of the supported chains so it is clear which ones are supported.

[piotr-roslaniec]

Since @nucypher/taco-web depends on @nucypher/contracts for contract compatibility, we may want to re-use (re-export) a list of supported networks from there.