docs: add comment explaining widget value store dom widgets getter nuance (#9202)

Adds comment explaining nuance with the differing registration semantics
between DOM widget vs base widet.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9202-fix-widget-value-store-dom-widgets-getter-3126d73d365081368b94f048efb101fa)
by [Unito](https://www.unito.io)

src/lib/litegraph/src/widgets/BaseWidget.ts

@@ -140,6 +140,9 @@ export abstract class BaseWidget<TWidget extends IBaseWidget = IBaseWidget>
 
     this._state = useWidgetValueStore().registerWidget(graphId, {
       ...this._state,
+      // BaseWidget: this.value getter returns this._state.value. So value: this.value === value: this._state.value.
+      // BaseDOMWidgetImpl: this.value getter returns options.getValue?.() ?? ''. Resolves the correct initial value instead of undefined.
+      // I.e., calls overriden getter -> options.getValue() -> correct value (https://github.com/Comfy-Org/ComfyUI_frontend/issues/9194).
       value: this.value,
       nodeId
     })