feat: add EVM testnet chains (sepolia, base-sepolia, arbitrum-sepolia, optimism-sepolia, polygon-amoy)

[ygd58]

Closes #189

Summary

Adds named testnet chain entries to the KNOWN_CHAINS registry.

Chains added

Name	Chain ID
sepolia	eip155:11155111
base-sepolia	eip155:84532
arbitrum-sepolia	eip155:421614
optimism-sepolia	eip155:11155420
polygon-amoy	eip155:80002

Notes

These chains were already usable via CAIP-2 ID (e.g. eip155:84532) or bare chain ID (84532) due to the generic EVM namespace fallback in parse_chain. This PR adds friendly names so users can write base-sepolia directly in CLI commands and SDK calls.

Tests

Adds 7 unit tests covering name lookup, CAIP-2 lookup, and bare chain ID lookup. All 90 existing tests continue to pass.

[vercel]

@ygd58 is attempting to deploy a commit to the MoonPay Team on Vercel.

A member of the Team first needs to authorize it.

[0xultravioleta]

Thanks for adding the EVM testnets. The CAIP-2 ids all look correct and there's no collision with anything already in the registry, so the substance is good.

Two small things before this can merge:

• A missing trailing newline is tripping cargo fmt --check. Running cargo fmt --all locally should fix it.
• The supported-chains docs and the binding network tables need the matching rows for the new testnets, so the docs stay in sync with what the code supports.

Once those two are in I think this is ready. Thanks.

[ygd58]

Updated in the latest commit:

• cargo fmt --all applied
• Added testnet rows to the EVM Networks table in docs/07-supported-chains.md
• Added matching shorthand aliases to the Aliases section

[0xultravioleta]

Thanks, that's both points covered. The five testnet rows and the matching aliases are in docs/07-supported-chains.md, and the fmt fix is in the same commit. The build checks on PRs from forks need a maintainer to start the run, which I'll sort out on our side, then once they're green this is ready to merge. The Vercel mark you'll see is just the fork deploy-auth, nothing to worry about.