Allow binary to be configurable

[YarekTyshchenko]

taskwarrior-tui/src/app.rs

Line 214 in 4902ecd

let output = std::process::Command::new("task")

On my system task binary is already taken by Taskfile.dev, a make replacement.
It'd be nice if the binary could be configured with a path

[RedEtherbloom]

This could also be a good time/place to add additional taskwarrio-tui config options for taskwarrior options that should be added pre- or post- the options that taskwarrior-tui calls task with.

[maulik13]

In the same boat here. By using both Taskfile and Taskwarrior is causing a lot more trouble than I thought. I am now making a home grown solution to switch binary/path based on what I need. However, this option could have solved the issue easily.

I do not RUST, so I am not sure about creating a PR. But, happy to learn enough RUST do it if it is welcome.