Manipulate tasks from `:Outstanding` buffer

[b0dee]

:Outstanding virtual buffer is currently just a view, want the ability to use commands when in the buffer that locate the current line under the cursor and apply an action to it i.e. remove, mark complete

[b0dee]

Figure this should apply to all bujo buffers, needs slightly different handling between i.e.:

• outstanding buffer should find the file based on the nearest header
• in daily log should check for any presence of entry in monthly/future
• custom function for within daily to close habits in the monthly table (see #54)

Notes: Going to do this via commands:

• :MarkComplete
• :MarkCancelled

Don't delete on cancell, just replace the [ ] with [~] and also do ~~ on either side of the task to make it strikethrough Need to have a defined key (which should be customisable) for closed/cancelled/missed tasks