make polkadot-parachain chain-spec extension more relaxed (#4452)
A small step towards
https://forum.polkadot.network/t/polkadot-parachain-omni-node-gathering-ideas-and-feedback/7823
and #4352.
Many parachains use `camelCase` and/or `PascalCase`ing for their chain
spec extension. Sometimes the only reason polkadot-parachain cannot sync
them is because it cannot parse the chain spec extension. This PR
relaxes the requirement for the extension to be camel case.
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Co-authored-by: Branislav Kontur <[email protected]>