QmlDesigner: Set a sensible initial size for various views

Fixes: QDS-10493
Change-Id: Idfb49daa60e73a5ee12da0d418d5122b1b5f6e62
Reviewed-by: Qt CI Patch Build Bot <ci_patchbuild_bot@qt.io>
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>

src/plugins/qmldesigner/components/effectmaker/effectmakerwidget.cpp

@@ -109,6 +109,11 @@ void EffectMakerWidget::focusSection(int section)
     Q_UNUSED(section)
 }
 
+QSize EffectMakerWidget::sizeHint() const
+{
+    return {420, 420};
+}
+
 QString EffectMakerWidget::qmlSourcesPath()
 {
 #ifdef SHARE_QML_PATH