Refactor: CSS handling (#2344)

* refactor(css): only load base styles, add css task, cleanup exports
* style(base): add edge label bg
* refactor(css): use css-utils
* feat(core): add Panel component
* refactor(background): cleanup
* refactor(css-handling): cleanup

packages/core/src/styles/index.ts

@@ -0,0 +1,9 @@
+import { CSSProperties } from 'react';
+
+export const containerStyle: CSSProperties = {
+  position: 'absolute',
+  width: '100%',
+  height: '100%',
+  top: 0,
+  left: 0,
+};