[Onboarding] - Make Check Boxes functional

[Aaryan1203]

Desired Changes

We want to be able to click a checkbox on a subtask. When all checkboxes are checked off on a subtask, the CheckListTask is automatically checked off. Note: A CheckListTask CANNOT be checked off to automatically check off all the subtasks. A CheckListTask can only be checked off if it has just a description and no SubTasks.

We also want to indicate if a CheckListTask has been completed by marking it as darker gray and moving it to the bottom of the list

Acceptance Criteria

• There is a new frontend hook for toggleChecklist
• If a user has completed all subtasks within a CheckListTask, then the overarching CheckListTask will be automatically checked off.
• You can check off a CheckListTask that has no subtasks
• When a CheckListTask is complete, it turns gray
• When the user closes the drop-down, the completed task will fall to the bottom of the checklist

Screenshots (as needed)