Accept relayChain and paraId as alternative spellings

[tomaka]

Close #2360

[mergify]

Automatically approving tomaka's pull requests. This auto-approval will be removed once more maintainers are active.

[github-actions]

twiggy diff report

Difference in .wasm size before and after this pull request.

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 Delta Bytes │ Item
─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
        +202 ┊ <smoldot::chain_spec::structs::_::<impl serde::de::Deserialize for smoldot::chain_spec::structs::ChainSpecParachain>::deserialize::__FieldVisitor as serde::de::Visitor>::visit_bytes::h5d7b83dca78ecae8
         +40 ┊ <smoldot::chain_spec::structs::_::<impl serde::de::Deserialize for smoldot::chain_spec::structs::ChainSpecParachain>::deserialize::__FieldVisitor as serde::de::Visitor>::visit_str::h78ed973190004999
         +16 ┊ data[0]
        +258 ┊ Σ [3 Total Rows]

[melekes]

👍