offline-first

As a follow-up on GoogleChrome/workbox#2255

Library Affected:
workbox-window.

Browser & Platform:
TypeScript

Issue or Feature Request Description:
While a lot of the types can currently be imported, they do use the source filepaths, which could break at any point as SemVer does not (and should not) handle things like that.

So this, while curre

In Settings : 'Add a new side account' button

Step #2 in Side account creation

(a very light & quick version of onboarding, with only nickname step)
![side account mode copy](https://user-images.githubusercontent.com/37345040/99953009-dd7db900-2d80-11eb-9f6f-e

Here is an issues with detailed description: NekR/offline-plugin#77