Add set_color to ansicolor_sink

It is now possible again to set the color in the ansicolor_sink with set_color

include/spdlog/sinks/ansicolor_sink.h

@@ -29,20 +29,52 @@ public:
     ansicolor_sink(FILE* file): target_file_(file)
     {
         should_do_colors_ = details::os::in_terminal(file) && details::os::is_color_terminal();
-        colors_[level::trace] = "\033[36m"; // cyan;
-        colors_[level::debug] = "\033[36m"; // cyan;
-        colors_[level::info] = "\033[0m";// default color;
-        colors_[level::warn] = "\033[33m\033[1m"; // yellow_bold;
-        colors_[level::err] = "\033[31m\033[1m"; // red_bold;
-        colors_[level::critical] = "\033[1m\033[41m"; // bold_red_bg;
-        colors_[level::off] = "\033[0m"; //reset to default;
+        colors_[level::trace] = cyan;
+        colors_[level::debug] = cyan;
+        colors_[level::info] = reset;
+        colors_[level::warn] = yellow + bold;
+        colors_[level::err] = red + bold;
+        colors_[level::critical] = bold + on_red;
+        colors_[level::off] = reset;
     }
     virtual ~ansicolor_sink()
     {
         _flush();
     }
 
-    
+    void set_color(level::level_enum color_level, const std::string& color) {
+        std::lock_guard<Mutex> lock(base_sink<Mutex>::_mutex);
+        colors_[color_level] = color;
+    }
+
+    /// Formatting codes
+    const std::string reset = "\033[00m";
+    const std::string bold = "\033[1m";
+    const std::string dark = "\033[2m";
+    const std::string underline = "\033[4m";
+    const std::string blink = "\033[5m";
+    const std::string reverse = "\033[7m";
+    const std::string concealed = "\033[8m";
+
+    // Foreground colors
+    const std::string grey = "\033[30m";
+    const std::string red = "\033[31m";
+    const std::string green = "\033[32m";
+    const std::string yellow = "\033[33m";
+    const std::string blue = "\033[34m";
+    const std::string magenta = "\033[35m";
+    const std::string cyan = "\033[36m";
+    const std::string white = "\033[37m";
+
+    /// Background colors
+    const std::string on_grey = "\033[40m";
+    const std::string on_red = "\033[41m";
+    const std::string on_green = "\033[42m";
+    const std::string on_yellow = "\033[43m";
+    const std::string on_blue = "\033[44m";
+    const std::string on_magenta = "\033[45m";
+    const std::string on_cyan = "\033[46m";
+    const std::string on_white = "\033[47m";
 
 protected:
     virtual void _sink_it(const details::log_msg& msg) override