Add wave PVD files

[MatthewFlamm]

This is a zip file with the following structure:

wavy/
    wavy.pvd
    wavy/
        wavy00.vts
        wavy01.vts
        ...

The .vts files were generated with the following script:

import pyvista as pv
import numpy as np

x = np.arange(-10, 10, 0.25)
y = np.arange(-10, 10, 0.25)
x, y = np.meshgrid(x, y)
r = np.sqrt(x ** 2 + y ** 2)
z = np.sin(r)

# Create and structured surface
grid = pv.StructuredGrid(x, y, z)
pts = grid.points
# Update Z and write a frame for each updated position
nframe = 15
for i, phase in enumerate(np.linspace(0, 2 * np.pi, nframe + 1)[:nframe]):
    z = np.sin(r + phase).ravel()
    pts[:, -1] = z
    grid['z'] = z
    grid.save(f"wavy{i:02}.vts")

The .pvd file was created manually.

wavy.pvd

<?xml version="1.0" encoding="UTF-8"?>
<VTKFile type="Collection" version="0.1" byte_order="LittleEndian" compressor="vtkZLibDataCompressor">
    <Collection>
        <DataSet timestep="0.00000e+00" group="" part="0" file="wavy/wavy00.vts"/>
        <DataSet timestep="1.00000e+00" group="" part="0" file="wavy/wavy01.vts"/>

This is being used for pyvista/pyvista#1564.

The .pvd file can be read by Paraview: