Is it possible extrude faces along normals individually in OpenSCAD?
Extruding faces is only possible on 2D polygons. From a 3D object you cannot capture the face and extrude it. To extrude "faces" you would need to define the shape of the face and extend it in the third dimension of your choice. This way a 3D shape is created that could be concatenated (joined using e.g. union) to the original shape. For the extrusion, the function linear_extrude is available:

linear_extrude(height = fanwidth, center = true, convexity = 10, twist = -fanrot, slices = 20, scale = 1.0, $fn = 16) {...}