feat: add Polkadot SDK JSON-RPC methods documentation

[F-OBrien]

Description

This PR adds a JSON-RPC reference for Polkadot SDK based chains. It includes two methods polkadot_signTransaction and SignerPayloadRaw and aligns with the polkadot examples https://docs.reown.com/advanced/multichain/polkadot/dapp-integration-guide

Tests

• - Ran the changes locally with Docusaurus. and confirmed that the changes appear as expected.
• - Applied the corrections suggested by Cspell on the .mdx files with changes.

Preview/s

https://reown-docs-git-fork-f-obrien-main-reown-com.vercel.app/advanced/multichain/rpc-reference/polkadot-sdk-rpc

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
reown-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Feb 5, 2025 10:33pm

[rtomas]

@F-OBrien thanks for the contribution.
Would you min fixing the sidebars.js modifications ?

[F-OBrien]

@F-OBrien thanks for the contribution. Would you min fixing the sidebars.js modifications ?

Looks like when I saved the change to sidebar.js modifications my IDE applied your prettier rules from .prettierrc.json. I've reverted them

[F-OBrien]

@rtomas just tagging in case you didn't see I updated. Let me know if you meant something else?

[F-OBrien]

@rohit-710 Was there a reason this wasn't merged other than sitting there for so long? Looking at the published docs I still don't see a JSON-RPC reference for Polkadot/Substrate based chains which this PR was adding?

[rohit-710]

Hey @F-OBrien, there were a couple of conflicts on this PR that was blocking me from approving and merging this PR. Can you please re-open this PR again?

Our docs went through a migration so a big majority of the structure and files have changed.