fix(CssManager): Make CssManager a singleton and export the shared instance via getSingleton; update tests and dependencies

ts/00_commitinfo_data.ts

@@ -3,6 +3,6 @@
  */
 export const commitinfo = {
   name: '@design.estate/dees-element',
-  version: '2.1.2',
+  version: '2.1.3',
   description: 'A library for creating custom elements extending the lit element class with additional functionalities.'
 }