TextEditor: Debounce update_preview() in on_change event

This avoids lag spikes when undoing/redoing large chunks of HTML/CSS
with the HTML preview open. This had been bugging me when reducing
LibWeb issues in the text editor. The debounce timeout is 100ms
so the delay should not be noticeable.

Userland/Applications/TextEditor/MainWidget.cpp

@@ -11,6 +11,7 @@
 #include <AK/URL.h>
 #include <Applications/TextEditor/TextEditorWindowGML.h>
 #include <LibConfig/Client.h>
+#include <LibCore/Debounce.h>
 #include <LibCore/File.h>
 #include <LibCpp/SyntaxHighlighter.h>
 #include <LibDesktop/Launcher.h>
@@ -63,9 +64,10 @@ MainWidget::MainWidget()
     else
         VERIFY_NOT_REACHED();
 
-    m_editor->on_change = [this] {
+    m_editor->on_change = Core::debounce([this] {
         update_preview();
-    };
+    },
+        100);
 
     m_editor->on_modified_change = [this](bool modified) {
         window()->set_modified(modified);