Document transaction discovery problem

[perama-v]

archors describes an architecture where an archive node is distributed at the block level (bundles containing all the state required to execute the bloc, and accompanying proofs).

A user can just download the blocks that are relevant to them.

How do they know which blocks? This is a discovery problem cleverly solved by the UnchainedIndex https://github.com/TrueBlocks/trueblocks-core:

chifra list my_address

Related, if the discovery problem is solved by a JSON-RPC method on archive nodes themselves (https://github.com/perama-v/eth_getAddressAppearances), then whatever distribution system
for distributing the archive node data (e.g., portal network), may also want to include a native version of this index of address appearances (holding a portion of the index, as determined by their node_id).

This should be included in docs