Enhancement - Filter for Today, Upcoming

[virgil9306]

Thanks for your work on this project.

So far it is the closest thing to my ideal task manager because it can be combined with the extensibility of Tiddlywiki there are so many possibilities.

I think that it would also be really helpful to have a simple string-based filter (based on fields) for hiding / showing items based on different projects, or date ranges (not just "Today" and "Upcoming" but custom date ranges).

[virgil9306]

Moved to #61