Preallocating multi-dimensioanal sequence i.e. variable size array

`sequtils` module is ready

Preallocating multi-dimensioanal sequence i.e. variable size array

You create your own type. In general if down the line it's all the same type, you should create a multi-dimensional view / tensor / ndarray. Here is a 50-lines example:

Preallocating multi-dimensioanal sequence i.e. variable size array

Preallocating multi-dimensioanal sequence i.e. variable size array

How to preallocate multi-dimensioanal sequence, as found only for single dimension e.g. newSeq[string](https://forum.nim-lang.org/7) ? Please shed the light on such nitty gritty data operation thanks in advance