[Feature]: Add in-progress/focus status to VS Code extension

[thombruce]

Feature request

The exclamation mark character is ideal for this, as it is easily accessible on the keyboard and is the first alphabetically of all keyboard-accessible characters, meaning that "focus" items will be sorted to the top of the list.

Consider also adding obsolete items denoted by a tilde (which sorts last alphabetically).

See this list (alphabetised) for example:

! (A) 2024-06-07 2024-06-30 This is a focus item with a priority, created date and due date
! (A) 2024-06-07 This is a focus item with a priority and created date
! (A) This is a focus item with a priority
! 2024-06-07 2024-06-30 This is a focus item with a created date and due date
! 2024-06-07 This is a focus item with a created date
! This is a focus item
(A) 2024-06-07 2024-06-30 This is an item with a priority, created date and due date
(A) 2024-06-07 This is an item with a priority and created date
(A) This is an item with a priority
2024-06-07 2024-06-30 This is an item with a created date and due date
2024-06-07 This is an item with a created date
This is an item
x (A) 2024-06-08 2024-06-07 2024-06-30 This is a completed item with a priority, completion date, created date and due date
x (A) 2024-06-08 2024-06-07 This is a completed item with a priority, completion date and created date
x (A) This is a completed item with a priority
x 2024-06-08 2024-06-07 2024-06-30 This is a completed item with a completion date, created date and due date
x 2024-06-08 2024-06-07 This is a completed item with a completion date and created date
x This is a completed item
~ (A) 2024-06-07 2024-06-30 This is an obsolete item with a priority, created date and due date
~ (A) 2024-06-07 This is an obsolete item with a priority and created date
~ (A) This is an obsolete item with a priority
~ 2024-06-07 2024-06-30 This is an obsolete item with a created date and due date
~ 2024-06-07 This is an obsolete item with a created date
~ This is an obsolete item

Code of Conduct

• [X] I agree to follow this project's Code of Conduct

[thombruce]

Styling suggestions:

The easiest modification we can make to focus items is to bold their text. We could also modify their colors for greater vibrancy, but this would be additional work.

For obsolete items, I suggest a strikethrough (similar to completed items), as well as to lower their opacity even further. A case of "we really want to ignore these - let's make them less visible". Naturally, do not lower their opacity so much that they become illegible.

[thombruce]

When this is done, move on to #109