Implement anchor and fix bugs with rigid body (#27)

Co-authored-by: Eric NGUYEN <enguyen@techform.fr>
Reviewed-on: https://git.siklos-chaneru.duckdns.org/Siklos/svg-layout-designer-react/pulls/27

src/utils/default.ts

@@ -33,6 +33,7 @@ export const DEFAULT_MAINCONTAINER_PROPS: IProperties = {
   width: DEFAULT_CONFIG.MainContainer.Width,
   height: DEFAULT_CONFIG.MainContainer.Height,
   isRigidBody: false,
+  isAnchor: false,
   fillOpacity: 0,
   stroke: 'black'
 };