Enable support for Pop-out module (workaround)

[zithith]

Is your feature request related to a problem? Please describe.
When using the Pop-Out! module, the side tabs approach doesn't work.

Describe the solution you'd like
Add support for pop-out (make the various tabs useable while the sheets are not in the FoundryVTT window). This will be a quick workaround for those using the module for now: add in a toggle setting for side tabs on the character sheets as we have for the item sheets.

Describe alternatives you've considered
A fix that preserves the side tabs may be possible but will need more investigation.

Version
0.2.1

Checklist:

• I have searched the existing issues to ensure this feature has not already been requested.