Changed ToolbarContainer's position element to be absolute - #7197

Fixes #7197

Summary

I was following the docs and wanted to mount decap inside of a div on my page, this worked good on the landing page of decap but did not work once I was on an editing page. The editor toolbar had a fixed position to the top so it would come out of my div and cover the custom header that I had made.

Test plan

I ran the tests using npm, at first they failed since the editor toolbar did not match the snapshot but since changing the component was what was intended, I updated the snapshot and the tests passed. (there was a warning that was also present before my change)

Screenshots before my change (I have decap mounted inside of a div that only covers 90% width of the page and has a header and footer above and below)
Before Change (ToolbarContainer has a position of fixed)

AfterChange (ToolbarContainer has a position of absolute)

Checklist

Please add a x inside each checkbox:

• I have read the contribution guidelines.

A picture of a cute animal (not mandatory but encouraged)