message: Add: `core` purser signer `signMessage` class method
diff: @@ -6,9 +6,7 @@ import {
  DESCRIPTORS,
  } from './defaults';
  -import type {
  - WalletArgumentsType,
  -} from './flowtypes';
  +import type { WalletArgumentsType } from './flowtypes';
  const { GENERIC_PROPS } = DESCRIPTORS;
  @@ -27,7 +25,12 @@ export default class PurserSigner extends Signer {
  ...GENERIC_PROPS,
  },
  getAddress: {
  - value: async () => purserWalletInstance.address,
  + value: async (): Promise<string> => purserWalletInstance.address,
  + ...GENERIC_PROPS,
  + },
  + signMessage: {
  + value: async (message: string): Promise<string> =>
  + purserWalletInstance.signMessage({ message }),
  ...GENERIC_PROPS,
  },
  });
  