Hierarchical sort

- an option for Sort Lines action

Input:

- a2
    -a2 b3
    -a2 b1
    -a2 b2
- a1
    -a1 b2
        -a1 b2 c2
        -a1 b2 c3
        -a1 b2 c1
    -a1 b3
    -a1 b1
        -a1 b1 c3
        -a1 b1 c4
        -a1 b1 c1

        -a1 b1 c6
        -a1 b1 c2
        -a1 b1 c5

✔️Hierarchical sort output:

- a1
    -a1 b1
        -a1 b1 c1
        -a1 b1 c2
        -a1 b1 c3
        -a1 b1 c4
        -a1 b1 c5
        -a1 b1 c6
    -a1 b2
        -a1 b2 c1
        -a1 b2 c2
        -a1 b2 c3
    -a1 b3
- a2
    -a2 b1
    -a2 b2
    -a2 b3

✔️or with Group by level and blank lines enabled:

- a1
    -a1 b1
        -a1 b1 c1
        -a1 b1 c3
        -a1 b1 c4

        -a1 b1 c2
        -a1 b1 c5
        -a1 b1 c6
    -a1 b2
        -a1 b2 c1
        -a1 b2 c2
        -a1 b2 c3
    -a1 b3
- a2
    -a2 b1
    -a2 b2
    -a2 b3

❌Normal sort output:

- a1
    - a2
    -a1 b1
    -a1 b1 c1
-a1 b1 c2
    -a1 b1 c3
        -a1 b1 c4
        -a1 b1 c5
        -a1 b1 c6
    -a1 b2
    -a1 b2 c1
        -a1 b2 c2
        -a1 b2 c3
        -a1 b3
        -a2 b1
        -a2 b2
        -a2 b3