Docs: added a readme file about the tool we use to edit our object diagrams.
Docs: added a readme file about the tool we use to edit our object diagrams.

nickerso/libcellml,hsorby/libcellml,hsorby/libcellml,nickerso/libcellml,hsorby/libcellml,MichaelClerx/libcellml,cellml/libcellml,cellml/libcellml,cellml/libcellml,nickerso/libcellml,nickerso/libcellml,MichaelClerx/libcellml,MichaelClerx/libcellml,hsorby/libcellml,cellml/libcellml