Increase offset of style preview

[rmzelle]

The current preview overlays are positioned very close to the left, so there is only a very small mouse target for the covered styles (just two letters wide):

Moving the overlays a little to the right would help a lot, I think.

[rmzelle]

(it's currently difficult to switch from the "3 Biotech" preview to the "3D Printing in Medicine" preview by sliding the cursor downwards)

[rmzelle]

I'm also having issues in Chrome with the vertical positioning, with the top of the preview being cut off:

[dstillman]

Increased offset is live

[dstillman]

I can reproduce the cut-off-top issue when filtered to APA.

[dstillman]

Seems like, for the cut-off issue, Drop might do the positioning incorrectly when the container/page ends? So it flips the popup up even though there's a lot more room on the page. This is more pronounced after a70db1f.