fix docs example (#250)

* fix docs example

* Update src/methods/polygonize.jl

---------

Co-authored-by: Anshul Singhvi <[email protected]>

Author: gaelforget

src/methods/polygonize.jl

@@ -19,7 +19,8 @@ polygonize
 
 Here's a basic example, using the `Makie.peaks()` function.  First, let's investigate the nature of the function:
 ```@example polygonize
-using Makie, GeometryOps
+using Makie, CairoMakie, GeoInterfaceMakie
+using GeometryOps
 n = 49
 xs, ys = LinRange(-3, 3, n), LinRange(-3, 3, n)
 zs = Makie.peaks(n)