Fix wording and duplicate code in embeddable example plugin

Signed-off-by: abbyhu2000 <abigailhu2000@gmail.com>

Author: abbyhu2000

examples/embeddable_examples/public/searchable_list_container/searchable_list_container_component.tsx

@@ -82,7 +82,6 @@ export class SearchableListContainerComponentInner extends Component<Props, Stat
       const output = props.embeddable.getChild(id).getOutput();
       hasMatch[id] = hasHasMatchOutput(output) && output.hasMatch;
     });
-    props.embeddable.getChildIds().forEach((id) => (checked[id] = false));
     this.state = {
       checked,
       hasMatch,

examples/embeddable_explorer/public/list_container_example.tsx

@@ -51,6 +51,7 @@ import {
 import { SearchableContainerInput } from '../../embeddable_examples/public/searchable_list_container/searchable_list_container';
 import { TodoInput } from '../../embeddable_examples/public/todo';
 import { MultiTaskTodoInput } from '../../embeddable_examples/public/multi_task_todo';
+import { HelloWorldEmbeddable } from '../../embeddable_examples/public/hello_world/hello_world_embeddable';
 
 interface Props {
   listContainerEmbeddableFactory: ListContainerFactory;
@@ -164,6 +165,15 @@ export function ListContainerExample({
               The first HelloWorldEmbeddable does not emit the hasMatch output variable, so the
               container chooses to hide it.
             </p>
+            <p>
+              Type some strings in the search bar, and press Check matching button. If the search
+              string matches with any strings from the title or the description of the children
+              embeddables, the child embeddable&#39;s check box will be checked. Noted that the
+              search filter is case sensitive. However, even if the search string matches with the
+              strings in the HelloWorldEmbeddable, its check box will not be checked because of the
+              reason explained above. If we click Delete checked, all the selected child embeddables
+              will be deleted from the container.
+            </p>
 
             <p>
               Check out the &quot;Dynamically adding children&quot; section, to see how to add