Add nodes for modifying vector paths #2817

Similar to how Instance Index and Instance Position input nodes work, but for paths. See for example Blender's Position Node:
https://docs.blender.org/manual/en/latest/modeling/geometry_nodes/geometry/read/position.html

This will allow the displacement of points in a path. One should also be able to modify the color and weight along the path.

Proposed nodes:

• Path Index
• Path Position
• Path Color
• Path Weight

Each of them should have a corresponding setter node, and/or be allowed as input to the Transform and Stroke nodes.
https://docs.blender.org/manual/en/latest/modeling/geometry_nodes/geometry/write/set_position.html

Down the road bezier handles should be accessible too. The more access to path data the better.