Clarify network-specific owner address discovery for PR #2 submissions

[Copilot]

• Context: PR Add ownership data for Polkadot, Kusama, and Westend parachains #2 stalled on Owner account population because the submitter did not know which addresses to use across Polkadot/Kusama/Westend.
• What changed:
  • README guidance: Added explicit account-discovery steps in the Notice section:
    1. open Polkadot.js Apps, 2) switch target network, 3) copy address from Accounts.
  • SS58 clarification: Documented that the same keypair renders different SS58 addresses per network and linked Subscan format transform for conversion.
  • Scope: Docs-only; no parachain JSON payload changes.

- If you are not sure which address is yours:
  1. Open Polkadot.js Apps and switch to the target network (Polkadot / Kusama / Westend).
  2. Go to Accounts and copy your address for that network.
  3. The same wallet can have different address formats on different networks (different SS58 prefixes).

Checklist

• Use the owner account that submitted registrar_reserve to sign the project information, and fill in the signature.
• After each update of the project information, please sign the latest data and submit the signature.
• Add a description for your pr, the description includes the original data.
• Fill up the signature of the original data, signature account to Signature Auto check.

Signature Auto check

Para ID Owner & Signature Account:
<REPLACE THE OWNER>

Data that needs to be signed:
file

Signature Hash: <REPLACE THE SIGNATURE>