OpenVR: Add note about how to enable interactions

For the interaction to work in the OpenVR examples,
it is required to copy the action/manifest .json files
to the working directory. This adds an according note
to the description of these examples

src/Cxx/GeometricObjects/OpenVRCone.md

 ### Description
 
 This example demonstrates rendering of a Cone in OpenVR.
+
+Note that for the interactions to work in VTK >= 9.1, you will have to copy the .json manifest files from the
+subfolder Rendering/OpenVR in VTK's source to the working directory in which the tests are run!
\ No newline at end of file

src/Cxx/GeometricObjects/OpenVRCube.md

 ### Description
 
 This example demonstrates rendering of a Cube in OpenVR.
+
+Note that for the interactions to work in VTK >= 9.1, you will have to copy the .json manifest files from the
+subfolder Rendering/OpenVR in VTK's source to the working directory in which the tests are run!
\ No newline at end of file

src/Cxx/GeometricObjects/OpenVRCylinder.md

 ### Description
 
 This example demonstrates rendering of a Cylinder in OpenVR.
+
+Note that for the interactions to work in VTK >= 9.1, you will have to copy the .json manifest files from the
+subfolder Rendering/OpenVR in VTK's source to the working directory in which the tests are run!
\ No newline at end of file

src/Cxx/GeometricObjects/OpenVRFrustum.md

 ### Description
 
 VTK + OpenVR Frustrum Example
+
+Note that for the interactions to work in VTK >= 9.1, you will have to copy the .json manifest files from the
+subfolder Rendering/OpenVR in VTK's source to the working directory in which the tests are run!
\ No newline at end of file

src/Cxx/GeometricObjects/OpenVROrientedArrow.md

 ### Description
 
 VTK + OpenVR OrientedArrow example.
+
+Note that for the interactions to work in VTK >= 9.1, you will have to copy the .json manifest files from the
+subfolder Rendering/OpenVR in VTK's source to the working directory in which the tests are run!
\ No newline at end of file

src/Cxx/GeometricObjects/OpenVROrientedCylinder.md

 ### Description
 
 VTK + OpenVR OrientedCylinder example.
+
+Note that for the interactions to work in VTK >= 9.1, you will have to copy the .json manifest files from the
+subfolder Rendering/OpenVR in VTK's source to the working directory in which the tests are run!
\ No newline at end of file

src/Cxx/GeometricObjects/OpenVRSphere.md

 ### Description
 
-This example demonstrates rendering of Sphere in OpenVR (HTC Head-Mounted Display).
+This example demonstrates rendering of a Sphere in OpenVR.
+
+Note that for the interactions to work in VTK >= 9.1, you will have to copy the .json manifest files from the
+subfolder Rendering/OpenVR in VTK's source to the working directory in which the tests are run!
\ No newline at end of file

src/Cxx/GeometricObjects/OpenVRTessellatedBoxSource.md

 ### Description
 
 VTK + OpenVR TessellatedBoxSource example.
+
+Note that for the interactions to work in VTK >= 9.1, you will have to copy the .json manifest files from the
+subfolder Rendering/OpenVR in VTK's source to the working directory in which the tests are run!
\ No newline at end of file