Reorganize issues

- Remove issue types
- Use labels or project custom fields to store issue metadata
- What do we want to store?
  - Priority
    - Is this needed?
  - State
    - Gathering interest
    - Planning
    - Ready to implement
    - Later (backlog)
  - Good first issue
  - Epic
    - A larger idea, encompassing multiple tasks
    - Shows the upcoming features of the app