Constrain proportions

We introduced the "Constrain proportions" feature to the scale property to maintain the ratio between width and height when you resize a layer. Hover over the lock icon next to the Scale property for the new tooltip and click to enable or disable.
Fixes & Improvements
- Renamed the converter utilities and updated their icons for clarity.
- Fixed a bug that affected the Drag Anchor tool.
- Fixed a bug that caused the canvas to disappear.