Create files for SVG and add svg.h

Histogram/svg.cpp

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+

Histogram/svg.h

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+#pragma once
+#include <iostream>
+#include <string>
+#include <vector>
+
+void svg_begin(double width, double height);
+void svg_end();
+void svg_rect(double x, double y, double width, double height, std::string stroke = "black", std::string fill = "black");
+void svg_text(double left, double baseline, std::string text);