PMP - add isotropic remeshing examples to the doc (#8655)

## Summary of Changes

For no reason, these examples where present but not available from the
documentation web pages.

## Release Management

* Affected package(s): PMP
* License and copyright ownership: unchanged

Polygon_mesh_processing/doc/Polygon_mesh_processing/examples.txt

@@ -19,6 +19,10 @@
 \example Polygon_mesh_processing/refine_fair_example.cpp
 \example Polygon_mesh_processing/mesh_slicer_example.cpp
 \example Polygon_mesh_processing/isotropic_remeshing_example.cpp
+\example Polygon_mesh_processing/isotropic_remeshing_of_patch_example.cpp
+\example Polygon_mesh_processing/isotropic_remeshing_with_allow_move.cpp
+\example Polygon_mesh_processing/isotropic_remeshing_with_custom_sizing_example.cpp
+\example Polygon_mesh_processing/isotropic_remeshing_with_sizing_example.cpp
 \example Polygon_mesh_processing/interpolated_corrected_curvatures_SM.cpp
 \example Polygon_mesh_processing/interpolated_corrected_curvatures_PH.cpp
 \example Polygon_mesh_processing/interpolated_corrected_curvatures_vertex.cpp
@@ -48,5 +52,4 @@
 \example Polygon_mesh_processing/remesh_almost_planar_patches.cpp
 \example Polygon_mesh_processing/sample_example.cpp
 \example Polygon_mesh_processing/soup_autorefinement.cpp
-\example Polygon_mesh_processing/isotropic_remeshing_with_allow_move.cpp
 */