Transforms (2D,3D) work without prefix in Opera 23
Update css-variables.json

Added MDN article
Update css-variables.json
data update
Merge pull request #604 from mpopp75/opera-transforms

Transforms (2D,3D) work without prefix in Opera 23
Merge pull request #607 from J0WI/patch-1

Update css-variables.json
data update