Add date type support in cache responses
Mongo only supports dates with time (not date alone) because of bson. 
So the `date` python type from `date32` pyarrow type couldn't be saved in mongo.

I fixed it by saving the `date` the same way as `string` objects.

Fix https://github.com/huggingface/datasets-server/issues/86

e.g. in first-rows for [aborruso](https://huggingface.co/aborruso)[/pnrr](https://huggingface.co/datasets/aborruso/pnrr)
```json
{
  "dataset": "__DUMMY_DATASETS_SERVER_USER__/pnrr",
  "config": "default",
  "split": "train",
  "features": [
    {
      "feature_idx": 0,
      "name": "Programma",
      "type": {
        "dtype": "string",
        "_type": "Value"
      }
    },
    ...
    {
      "feature_idx": 50,
      "name": "Data di Estrazione",
      "type": {
        "dtype": "date32",
        "_type": "Value"
      }
    }
  ],
  "rows": [
    {
      "row_idx": 0,
      "row": {
        "Programma": "PNRR",
        ...
        "Data di Estrazione": "2023-06-13"
      },
      "truncated_cells": []
    },
    ...
    ]
}
```

EDIT: also added support for time, timedelta and decimal

I also checked binary but it is already supported, though its format is not ideal (we get a list of integers from mongo)
Add date type support in cache responses: Mongo only supports dates with time (not date alone) because of bson. 
So the `date` python type from `date32` pyarrow type couldn't be saved in mongo.

I fixed it by saving the `date` the same way as `string` objects.

Fix https://github.com/huggingface/datasets-server/issues/86

e.g. in first-rows for [aborruso](https://huggingface.co/aborruso)[/pnrr](https://huggingface.co/datasets/aborruso/pnrr)
```json
{
  "dataset": "__DUMMY_DATASETS_SERVER_USER__/pnrr",
  "config": "default",
  "split": "train",
  "features": [
    {
      "feature_idx": 0,
      "name": "Programma",
      "type": {
        "dtype": "string",
        "_type": "Value"
      }
    },
    ...
    {
      "feature_idx": 50,
      "name": "Data di Estrazione",
      "type": {
        "dtype": "date32",
        "_type": "Value"
      }
    }
  ],
  "rows": [
    {
      "row_idx": 0,
      "row": {
        "Programma": "PNRR",
        ...
        "Data di Estrazione": "2023-06-13"
      },
      "truncated_cells": []
    },
    ...
    ]
}
```

EDIT: also added support for time, timedelta and decimal

I also checked binary but it is already supported, though its format is not ideal (we get a list of integers from mongo)