Idea: Add priority for tasks similar as todo.txt

[dwettstein]

The format of todo.txt includes an optional priority for tasks (todotxt_format).

As a project manager or product owner it can be very important to set a priority on tasks.

Suggestion: Add priority similar as todo.txt

Example:

- [ ] Feature xy
  - [ ] (A) High priority sub-task
  - [ ] (C) Low priority sub-task
- [x] (P1) Another, already done task with a different priority naming