Use markdown instead of HTML code
Rename images to clarify what they describe
Rename all images to remove mx prefixes

model-and-cells.md: remove ref to mxGraph
model-and-cells.md: layers example
model-and-cells.md: finish "The Model Change Methods" (end line 141)
model-and-cells.md: add todo

…uce a docusaurus plugin to create static redirects