expose EdgewareTypes via index.ts

[jacogr]

This allows users to shortcut the process a tiny bit, i.e. on the polkadot-js side doing this at least in two places (and probably don't need to know much about the internal modules are diff. parts) -

• extension (new) - https://github.com/polkadot-js/extension/pull/153/files#diff-238e61a7406f819b33ad6ccdfc104c99R7
• apps UI (existing) - https://github.com/polkadot-js/apps/blob/master/packages/react-api/src/overrides/spec/edgeware.ts#L5

This would allow to shortcut this and just do an import { EdgewareTypes } from '@edgeware-node-types/dist';