Add a timer

[kjk]

We're kind of a productivity app so add a Start timer command.

This is to measure how long a given task takes:

• start a timer e.g. named implement timer
• shows up in upper right corner
• can be paused, cancelled, mark as done and renamed

Maybe remember all non-cancelled timers with date, start time, name, duration

Maybe auto-add done timers to daily journal for current day e.g. as:

task: implement timer, dur: 1 hr 37 min, start: 17:37

The format could be editable.

This is to record timer tasks.

Related: pomodoro timer?