Command or option to transform blocks into TODOs

[andreoliwa]

Problem

As a user converting old Markdown I want to quickly add the same TODO prefixes to several lines at once, in order to avoid manual editing of converted lines.

Possible solution

1. Add a todo command.
2. ...or a --todo option on the outline command?
3. ...or both?
4. By default, add TODO to new blocks.
5. Allow choosing between TODO, DOING, DONE, NOW and LATER.
6. If run from the todo command: should it also convert to outline before adding the prefix?
7. By default, add the prefix on all blocks. If possible (or another issue), use fzf or something to select which headers should become TODOs.