Contributed:

• Add support for new Frontier AccountId20 mapping (Thanks to https://github.com/koushiro)
• Adjust MMR RPCs & runtime calls to align with latest (Thanks to https://github.com/Lederstrumpf)

Changes:

• Use Promise resolve/reject to track state in typegen on-chain metadata retrievals
• Adjust signing header retrieval, catering for discarded state fallbacks
• Add support for ParachainHost v4 runtime calls
• Basic support for markdown generation for different chains (only Kusama & Polkadot currently added)
• Add not-to-be-used ISize type support (same as USize, throwing on use - added for completeness)
• Ensure AccountId20.eq does not fail on null/undefined inputs
• Expand tests around toU8a() where the isBare flag is is being used
• Update to latest Polkadot, Kusama & Substrate metadata