Node.js checks package.json exports before filesystem, so the
mkdir+echo shim didn't work. Now patches the exports map with
node -e to add ./substrate pointing to pezkuwi augmentation.
- Add missing @polkadot/rpc-augment alias to @pezkuwi/rpc-augment
- Create substrate shim for @polkadot/api-augment/substrate that
re-exports @pezkuwi/api-augment's pezkuwi augmentation, fixing
ERR_PACKAGE_PATH_NOT_EXPORTED when @subql/node requires it