Maximal nested depth

[david-littlefarmer]

Description

Added maximal nested depth, to prevent infinite loop as reported in this bug #25.
Default value is 20

Tested with:

type Infinite struct {
	ID   int
	This *Infinite
}

func printInfiniteLoop() {
	opts := &devslog.Options{
		MaxNestedDepth: 10,
	}

	logger := slog.New(devslog.NewHandler(os.Stdout, opts))

	v := Infinite{ID: 123}
	v.This = &v
	logger.Info("infinite", slog.Any("test", v))
}

Checklist

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary