Feat: dark mode (#3652)

* feat(react/svelte): add dark mode defaults

* refactor(darkmode): minimap, edges, edge labels

* chore(style): edge label color

* feat(colorMode): add colorMode prop light/dark/system

* chore(examples): cleanup

* test(colorMode): add tests

* chore(base.css): add dark base

* chore(examples): cleanup

examples/react/src/App/routes.ts

@@ -1,5 +1,6 @@
 import Basic from '../examples/Basic';
 import Backgrounds from '../examples/Backgrounds';
+import ColorMode from '../examples/ColorMode';
 import ControlledUncontrolled from '../examples/ControlledUncontrolled';
 import ControlledViewport from '../examples/ControlledViewport';
 import CustomConnectionLine from '../examples/CustomConnectionLine';
@@ -62,6 +63,11 @@ const routes: IRoute[] = [
     path: 'backgrounds',
     component: Backgrounds,
   },
+  {
+    name: 'Color Mode',
+    path: 'color-mode',
+    component: ColorMode,
+  },
   {
     name: 'Cancel Connection',
     path: 'cancel-connection',