code: Add a docstring for numpy, scipy packages

.. this fixes a problem in CircuitPython where building the docs would say
"../shared-bindings/ulab/numpy/approx/index.rst: WARNING: document isn't included in any toctree"

code/numpy/numpy.c

@@ -29,6 +29,9 @@
 #include "poly/poly.h"
 #include "vector/vector.h"
 
+//| """Compatibility layer for numpy"""
+//|
+
 // math constants
 #if ULAB_NUMPY_HAS_E
 mp_obj_float_t ulab_const_float_e_obj = {{&mp_type_float}, MP_E};

code/scipy/scipy.c

@@ -22,6 +22,9 @@
 
 #if ULAB_HAS_SCIPY
 
+//| """Compatibility layer for scipy"""
+//|
+
 static const mp_rom_map_elem_t ulab_scipy_globals_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_scipy) },
     #if ULAB_SCIPY_HAS_OPTIMIZE_MODULE