feat: add isLean function

src/elements/core/dom.ts

@@ -3,6 +3,7 @@ export * from './dom/find-referenced-element.js';
 export * from './dom/get-document-writing-mode.js';
 export * from './dom/host-context.js';
 export * from './dom/input-element.js';
+export * from './dom/lean-context.js';
 export * from './dom/set-or-remove-attribute.js';
 export * from './dom/platform.js';
 export * from './dom/scroll.js';

src/elements/core/dom/lean-context.ts

@@ -0,0 +1,6 @@
+/**
+ * Checks if the body has the `sbb-lean` class.
+ */
+export function isLean(): boolean {
+  return document.body.classList.contains('sbb-lean');
+}