restore side-windowed.scad lost from previous commit

src/frames/pieces/side-windowed.scad

@@ -0,0 +1,23 @@
+/*
+ * SPDX-FileCopyrightText: © 2024 Brian S. Stephan <bss@incorporeal.org>
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+include <parameters.scad>
+include <components.scad>
+use <side.scad>
+use <side-inner-wall.scad>
+
+module windowed_side_frame_piece() {
+	difference() {
+		side_frame_piece();
+		// subtract frame wall window
+		translate([-frame_x/2, 0, 0])
+			cube([(frame_wall+panel_support_width)*2, frame_y-frame_mount_column_width*3.5,
+				frame_z-panel_z*3], center=true);
+		// subtract the inner wall area that will be provided by the other piece
+		side_inner_wall_frame_piece();
+	}
+}
+
+windowed_side_frame_piece();