Add option to auto-start timer when first opening the browser

[schmich]

From Thamizharasan M in Chrome Web Store review:

Sometime we forget to start this timer when we open chrome. If there is an option to auto start when the chrome starts, then it will be so helpful and I have seen this feature available in other extension.

Consider using chrome.runtime.onStartup.

[ghost]

Hi @schmich, would you still consider working on this feature? I am really in need of this feature, I could help out if it would be fine by you.

[DoctypeRosenthal]

duplicate of https://github.com/schmich/marinara/issues/11?