improve docstring

Author: ufechner7

src/wing_geometry.jl

@@ -61,6 +61,14 @@ end
     add_section!(wing::Wing, LE_point::PosVector, TE_point::PosVector, aero_input)
 
 Add a new section to the wing.
+
+# Arguments:
+- LE_point::PosVector: position of the point on the side of the leading edge
+- TE_point::PosVector: position of the point on the side of the leading edge
+- aero_input: Can be:
+  - :inviscid
+  - :lei_airfoil_breukels
+  - (:interpolations, (cl_interp, cd_interp, cm_interp))
 """
 function add_section!(wing::Wing, LE_point::Vector{Float64}, 
                      TE_point::Vector{Float64}, aero_input)