register function return a value

[benschac]

    const tx = await entropy.register({
      address: selectedUser.address,
      keyVisibility: 'Permissioned',
      freeTx: false,
    })

would be helpful if register(params: RegistrationParams): Promise<undefined>; was register(params: RegistrationParams): Promise<boolean>;

so developers do not need make a second api call to isRegistered: (address: Address) => Promise<boolean>; after initially registering a user.

[frankiebee]

closed by #264