Fix formatting bar

https://workflow.ghx.com/browse/VASS-237

The formatting bar sometimes obscures input text. Change is to adjust skidding to 0 so it rests above the reference. In this case, VEditor (top-start).

https://popper.js.org/docs/v2/modifiers/offset/

A subsequent change will come for phapp to bump version.

To verify:

1. Clone this repo: https://gitlab.com/lumere-public/lumere-ui then switch to this branch
2. In newly cloned lumere-ui repo, run npm link
3. in phapp repo, run npm link @lumere/lumere-ui
4. Then run ls to verify it's correct: npm ls @lumere/lumere-ui
5. Restart server
6. Go to a project: http://localhost:8000/projects/28689/#/
7. Update status

Expect: formatting bar is anchored to top of editor.