Improved collapse button clickable area

Author: alelievr

Assets/com.alelievr.NodeGraphProcessor/Editor/Resources/GraphProcessorStyles/BaseNodeView.uss

@@ -231,4 +231,17 @@ ParameterNodeView #controls EnumField > VisualElement > VisualElement {
 #BottomPortContainer
 {
     margin-top: -1px;
+}
+
+#title-button-container
+{
+    align-items: center;
+    align-content: center;
+}
+
+#collapse-button:
+{
+    width: 16px;
+    height: 16px;
+    margin: 4px;
 }