Adding a help ?

[lpatiny]

We should add somewhere the detailed help of OCL editor. Not sure if it should be here or in openchemlib-js

we have in fact 3 pages:

• https://docs.nmrium.org/help/ocl
• https://docs.nmrium.org/structure_assignment/ocl/atom-properties
• https://docs.nmrium.org/structure_assignment/ocl/stereochemistry