AST-62: Update docs/design.md
Extend https://git.astron.nl/RD/EveryBeam/-/blob/master/docs/design.md so as to be more specific on the most important classes and their inter-dependencies.
Edited by Jakob Maljaars
Extend https://git.astron.nl/RD/EveryBeam/-/blob/master/docs/design.md so as to be more specific on the most important classes and their inter-dependencies.