(Error handling skipped on init) CompleteAuth not triggered for init

[parlir]

When using the init flow it will skip over completeauth when errors occur and therefore error handling is skipped.

scenario is as follows:

1. User triggers init in code
2. authorize function sets SessionStorage with state_key here https://github.com/parlir/client-js/blob/master/src/smart.ts#L270
   and here https://github.com/parlir/client-js/blob/master/src/smart.ts#L303
3. Redirect happens (and user authorizes and is redirected back to where init was called)
4. Init called again post redirect and only checks for code and state (as opposed to other parameters such as error etc...
   https://github.com/parlir/client-js/blob/master/src/smart.ts#L758
5. State has been set on previous calls and so cache is set and init returns client swallowing the error in the process here
   https://github.com/parlir/client-js/blob/master/src/smart.ts#L768

I think a quick fix to this issue could be to check for error parameter and call the completeauth function if error parameter exists on step 4.

@vlad-ignatov I'm happy to open a PR for this let me know wyt.

[parlir]

Can confirm the following modifications on init function worked for me:

    const error = url.searchParams.get("error");

    // if error or (`code` and `state`) params are present we need to complete the auth flow
    if (error || code && state) {
        return completeAuth(env);
    }