Add Paseo AssetHub specs in the Polkadot Binary

As we move to **Paseo Asset Hub** (Polkadot testnet), could we embed its chain spec in the Polkadot binary so users can start a node with `--chain paseo-asset-hub` (or whatever name we finalize)? 

This would streamline docs for anyone running a node—and an ETH RPC proxy—on Paseo Asset Hub. 

Thanks!
