### SpriteSheet.ts
- modified SpriteSheetSpacingDimensions originOffset and margin to accept optional Vectors
- modified fromImageSource to test for instance of Vector and handle it properly, while maintaining backward compatibility
### SpriteSheetSpec.ts
- added test: `can be created from with spacing using vectors`
### Updated docs entry on Spritesheets to note that Vectors are now allowed
Ran locally and verified functionality using both vec() and new Vector
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Co-authored-by: Erik Onarheim <[email protected]>
