Add Polkadot integration

[0binna-oss]

Description

The Polkadot chain integration adds support for polkadot to the multichain-crypto-wallet. Key features include:

1. Initialization:

Establishes a connection to the polkadot network using a WebSocket RPC endpoint.

2. Wallet Generation:

Creates new wallets with sr25519 key pairs.

3. Balance Retrieval:

fetches account balances with address validation using ss58 format.

4. Disconnection:

Cleans up API and keyring instances to ensure proper resource management.

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• Any dependent changes have been merged and published in downstream modules.
• I ran npm run test and my test cases cover all the lines and branches of the added code.
• I ran npm run build with success.
• I have tested my code on the live network.
• I have checked the Deploy Preview and it looks correct.