Add developer documentation

[Niolon]

The example implementation index.html in demo seems to be too limited and/or hidden for people engaging with the project

• Developing with CifVis
  • Interacting with a CIF file (Blocks, entries, Loops)
  • Using CrystalViewer to display a structure. Where are the binding points for a self-developed graphical user interface
  • Understanding and using Filters to change the displayed structure
• Developing CifVis
  • The lay of the land
    • The individual folders
    • Hierachy of objects (What kind of functionality is located in the individual layers, dependencies)
  • Full JSDoc generated documentation of all components