Document localnet configuration values for near-cli-rs

[r-near]

Summary

Add documentation explaining the configuration values needed when setting up a localnet connection in near-cli-rs.

Context

This was requested in near/near-cli-rs#547, where @frol provided a detailed breakdown of all the localnet configuration options:

• wallet_url - URL for importing accounts from web wallet
• explorer_transaction_url - URL for transaction links
• linkdrop_account_id - Contract for creating subaccounts
• near_social_db_contract_account_id - NEAR Social metadata
• faucet_url - Service for creating new accounts
• fastnear_url - API for fetching staking pool delegations
• staking_pools_factory_account_id - Fallback for staking pool queries
• mpc_contract_account_id - MPC signing service

Most of these can be skipped or set to placeholder URLs for localnet, but this isn't documented anywhere.

Suggested Location

Either:

• docs/tools/cli.md under the "Configuration file" section
• docs/web3-apps/tutorials/localnet/run.md as part of the localnet setup guide

Reference

See the full explanation: near/near-cli-rs#547