Add sub-items to checklists

[Violet-RM]

Checklist

• [X] I made sure that there are no existing issues - open or closed - to which I could contribute my information.
• [X] I made sure that there are no existing discussions - open or closed - to which I could contribute my information.
• [X] I have read the FAQs inside the app (Menu -> About -> FAQs) and my problem isn't listed.
• [X] I have taken the time to fill in all the required details. I understand that the bug report will be dismissed otherwise.
• [X] This issue contains only one feature request.
• [X] I have read and understood the contribution guidelines.
• [ ] I optionally donated to support the Fossify mission.

Feature description

It would be useful to add sub-items to checklist notes.

Example:

• [ ] Fix the car
  • [x] Rotate the tires
  • [ ] Change the oil
• [x] Go to the store

Why do you want this feature?

It would help keep well ordered lists easily.

Additional information

No response