Add Kochanek Spline function

[tkoyama010]

Overview

Add Kochanek Spline function

See #1600

resolves #1600

Details

kochanek_spline = pv.KochanekSpline(
    points,
    continuity=[-1.0, -1.0, -1.0],
    tension=[0.0, 0.0, 0.0],
    bias=[0.0, 0.0, 0.0],
    n_points=1000,
)

[codecov]

Codecov Report

Merging #1603 (d079534) into main (ba6c84f) will increase coverage by 0.03%.
The diff coverage is 97.56%.

@@            Coverage Diff             @@
##             main    #1603      +/-   ##
==========================================
+ Coverage   90.04%   90.07%   +0.03%     
==========================================
  Files          69       69              
  Lines       13154    13195      +41     
==========================================
+ Hits        11845    11886      +41     
  Misses       1309     1309              

[akaszynski]

Made some minor changes. LGTM!