Support default exports of `iso` field declarations

[rbalicki2]

Problem

• We use this regex to match named exports of iso field declarations:

    static ref EXTRACT_ISO_LITERAL: Regex =
        Regex::new(r"(export const ([^ ]+) =\s+)?iso(\()?`([^`]+)`(\))?(\()?").unwrap();

• This does not support default exports of iso literals

Solution

• We should modify this regex to also support default exports of iso literals, and modify lines like import { PetSummaryCard as resolver } from '../../../PetSummaryCard.tsx'; to be import resolver from '../../../PetSummaryCard.tsx'; in cases where the user uses a default export
• We should also add some unit tests here!