Feature for uniform knot refinement

[FSchwar]

Overview

Using the insert_knots function for uniform knot refinements in arbitrary dimensions.

Addressed issues

Showcase

A short / one-liner example to highlight the (new) feature

import splinepy as _spp

example_spline = _spp.helpme.create.box(3, 1, 2)
example_spline = example_spline.bspline
example_spline.uniform_refine(degree_of_refinement = [1, 5], parametric_dimensions = [1, 2])
example_spline.show()

Checklists

• [ ] Documentations are up-to-date.
• [ ] Added example(s)
• [ ] Added test(s)

[j042]

maybe we can a simple test that checks number of elements. @OberGue can you add this in #348