More selection tools

[chchwy]

We need more selection tools, like a lasso and a polygonal lasso.

[J5lx]

Lasso tool issue: #118

[Jose-Moreno]

[2020] Let's leave this issue as a tracker for extra selection tools:
Note: We should open individual issues for each one, once they've been discussed

• Freehand / Lasso Selection build a lasso tool #118
• Polygonal Lasso Selection: Similar to the polyline
• Ellipse Selection
• Magic Wand / Eyedropper / Threshold value Selection: Clicking on any given RGBA value (included pure transparent values) would select an area defined by said value on the canvas and current frame
• Brush Selection (needs discussion): Would work by converting luminance values (B/W) or alpha values into a marching ants selection area.