Blockbench

## Fixes
* Fixed #3645 locked blueprint reference image not updating with view
* Fixed #3521 issue with weight painting on touch devices
* Fixed armature bone of different meshes used to highlight weights
* Improved performance of fill tool (paint bucket) (#3635, thanks @fuzorsilverbolt!)
* Optimized billboard rendering performance
* Fixed copy-pasting textures not working in the web app
* Fixed #3646 outliner folding-arrow update issue
* Potential fix for rare startup issue #3267
* Pressing enter in amend edit UI now confirms input, but does not close UI
* Fixed #3650 spline sliders do not support pressing modifier keys for decimal inputs
* Fixed spline getting random color on each amend
* Fixed #3647 texture context menu not working on iOS via long-press due to Safari change