Make possible to edit the GraphEdit's selection rect colors

doc/classes/GraphEdit.xml

@@ -316,6 +316,10 @@
 		</theme_item>
 		<theme_item name="reset" type="Texture">
 		</theme_item>
+		<theme_item name="selection_fill" type="Color" default="Color( 1, 1, 1, 0.3 )">
+		</theme_item>
+		<theme_item name="selection_stroke" type="Color" default="Color( 1, 1, 1, 0.8 )">
+		</theme_item>
 		<theme_item name="snap" type="Texture">
 		</theme_item>
 	</theme_items>

editor/editor_themes.cpp

@@ -1012,6 +1012,8 @@ Ref<Theme> create_editor_theme(const Ref<Theme> p_theme) {
 		theme->set_color("grid_major", "GraphEdit", Color(0.0, 0.0, 0.0, 0.15));
 		theme->set_color("grid_minor", "GraphEdit", Color(0.0, 0.0, 0.0, 0.07));
 	}
+	theme->set_color("selection_fill", "GraphEdit", theme->get_color("box_selection_fill_color", "Editor"));
+	theme->set_color("selection_stroke", "GraphEdit", theme->get_color("box_selection_stroke_color", "Editor"));
 	theme->set_color("activity", "GraphEdit", accent_color);
 	theme->set_icon("minus", "GraphEdit", theme->get_icon("ZoomLess", "EditorIcons"));
 	theme->set_icon("more", "GraphEdit", theme->get_icon("ZoomMore", "EditorIcons"));

scene/gui/graph_edit.cpp

@@ -777,14 +777,8 @@ void GraphEdit::_top_layer_draw() {
 	}
 
 	if (box_selecting) {
-		top_layer->draw_rect(
-				box_selecting_rect,
-				get_color("box_selection_fill_color", "Editor"));
-
-		top_layer->draw_rect(
-				box_selecting_rect,
-				get_color("box_selection_stroke_color", "Editor"),
-				false);
+		top_layer->draw_rect(box_selecting_rect, get_color("selection_fill"));
+		top_layer->draw_rect(box_selecting_rect, get_color("selection_stroke"), false);
 	}
 }
 

scene/resources/default_theme/default_theme.cpp

@@ -851,6 +851,8 @@ void fill_default_theme(Ref<Theme> &theme, const Ref<Font> &default_font, const
 	theme->set_stylebox("bg", "GraphEdit", make_stylebox(tree_bg_png, 4, 4, 4, 5));
 	theme->set_color("grid_minor", "GraphEdit", Color(1, 1, 1, 0.05));
 	theme->set_color("grid_major", "GraphEdit", Color(1, 1, 1, 0.2));
+	theme->set_color("selection_fill", "GraphEdit", Color(1, 1, 1, 0.3));
+	theme->set_color("selection_stroke", "GraphEdit", Color(1, 1, 1, 0.8));
 	theme->set_color("activity", "GraphEdit", Color(1, 1, 1));
 	theme->set_constant("bezier_len_pos", "GraphEdit", 80 * scale);
 	theme->set_constant("bezier_len_neg", "GraphEdit", 160 * scale);