some tests and initial json structure

cmd/test/main.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"fmt"
+
+	xlsx "github.com/tealeg/xlsx/v3"
+)
+
+func main() {
+	xls, err := xlsx.OpenFile("../../test/gwb-rechner_5_0_4_vollbilanz.xlsx")
+	fmt.Println("OpenFile err:", err)
+	sl, err := xls.ToSlice()
+	fmt.Printf("err: %v\n\n%#v", err, sl[1])
+}