Add command to generate Colors

Sources/FontToolCore/FontToolError.swift

@@ -16,12 +16,16 @@ enum FontToolError: Error {
         switch self {
         case .fcScan(let path, let code, let output):
             return """
+            [FontTool]
             Error while getting fontName (fc-scan --format %{postscriptname} \(path).
             fc-scan exit with \(code) and output is: \(output ?? "no output")
             """
             
         case .inputFolderNotFound(let inputFolder):
-            return "Input folder not found: \(inputFolder)"
+            return """
+            [ColorTool]
+            Input folder not found: \(inputFolder)
+            """
         }
     }
 }