u02: Add star tool skeleton

u02/include/star_tool.h

@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+#pragma once
+
+#include "tool_base.h"
+
+class star_tool : public tool_base {
+public:
+  star_tool(canvas_buffer &canvas);
+
+  void draw(int x0, int y0, int x1, int y1);
+
+  void set_text(std::stringstream &stream);
+};

u02/src/star_tool.cpp

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+// SPDX-License-Identifier: LGPL-3.0-or-later
+#include "star_tool.h"
+#include <cmath>
+#include <util.h>
+
+star_tool::star_tool(canvas_buffer &canvas) : tool_base(canvas) {
+  shape = TS_CIRCLE; // TODO: Use star for preview
+}
+
+void star_tool::draw(int x0, int y0, int x1, int y1) {}
+
+void star_tool::set_text(std::stringstream &stream) { stream << "Tool: Star"; }