Add a new OpenGL pyramid sample

This sample shows the use of modern OpenGL (3.2).

Closes #16910.

docs/doxygen/mainpages/samples.h

@@ -553,6 +553,8 @@ commands through the menu.
     Arrow keys rotate the cube. Space bar toggles spinning.
 @li @b isosurf Draws a surface by reading coordinates from a DAT file.
 @li @b penguin Draws a rotatable penguin by reading data from a DXF file.
+@li @b pyramid Draws a rotatable tetrahedron and some strings.
+    It uses OpenGL 3.2 Core Profile context.
 
 @sampledir{opengl}