Add .mat file for HDF5-TDMS-object unit tests to run.

- Adds scripts to reproduce this data, so in theory a new user can run a short MATLAB script to reproduce this
- Had a play with trying to get setup-matlab to run these scripts before the unit tests, but alas, no.

tdms/tests/unit/hdf5_io_tests/create_structure_array.m

@@ -0,0 +1,19 @@
+%% This script creates the structure_array.mat file for use in the hdf5 tests for reading in structure arrays.
+close all;
+clear;
+
+example_struct = struct();
+
+example_struct.double_no_decimal = 1.;
+example_struct.double_half = 0.5;
+example_struct.string = 'tdms';
+example_struct.boolean = true;
+example_struct.uint_345 = uint8(ones(3, 4, 5));
+example_struct.double_22 = [0.25, 0.5; 0.75, 1.];
+example_struct.complex_22 = [0., -1.i; 1.i, 0.];
+
+%% save variables to the file we need
+% Save the files to the expected filename for the unit tests to read the
+% data back in.
+
+save("structure_array.mat", "example_struct", "-v7.3");