Zy/109 script remember current location

[zheyxu]

Pull Request Details

What issue does this PR address

• SCRIPT: Remember current location in the scrolled script.

• Link to associated issue: #109

Checklist

Complete the check-list below to ensure your branch is ready for PR.

Flutter Style Guide: https://survivor.togaware.com/gnulinux/flutter-style.html

• [x] Screenshots included in linked issue
• [x] Changes adhere to the style and coding guideline
• [x] No confidential information
• [x] No duplicated content
• [ ] No lint check errors related to your changes (make prep or flutter analyze lib)
• [x] Pre-exisiting lint errors noted: [HERE]
• [ ] Integration test make qtest.tmp screenshot included in issue
• [x] Tested on device:
  • [ ] Linux
  • [x] MacOS
  • [ ] Windows
• [x] Added two reviewers

Finalising

Once PR discussion is complete and reviewers have approved:

• [ ] Merge dev into the branch
• [ ] Resolve any conflicts
• [ ] Add one line summary into CHANGELOG.md
• [ ] Bump appropriate version number in pubspec.yaml
• [ ] Push to git repository and review
• [ ] Merge PR into dev (gjwgit)