Merged PR 179: Fix bugs about flex and context menu (see desc) + disable hard rigid behavior + add missing properties to form + Clean up css

- Clean up some css class
- Fix wrong order when applying flex
- Fix Replace behavior not working because previous container was still existing
- Disable hard rigid behavior which disallow two container to overlap
- Add ENABLE_FLEX, ENABLE_HARD_RIGID ENABLE_SWAP
- Add missing form properties with dimensions
- Update readme

src/main.tsx

@@ -11,7 +11,10 @@ function RenderRoot(root: Element | Document): void {
   );
 }
 
+// Specific for Modeler apps
+// eslint-disable-next-line @typescript-eslint/no-namespace
 namespace SVGLayoutDesigner {
+  // eslint-disable-next-line @typescript-eslint/naming-convention
   export const Render = RenderRoot;
 }