view previous timers

[sunaku]

Hello,

Please add the ability to view previous (expired) timers. :watch: This would help me see what activities I have spent my time on, say, in the past week so that I may improve my time management. :notebook:

Thanks for your consideration.

[sunaku]

I have attached a pull request to this issue containing a patch that replaces the automatic clearing of timers on Chrome start with a button in the options page that must be manually pressed to clear timers.