feat: add Tabular field to structure

[ramfox]

CSV and xlsx are always considered Tabular.

Json is where this get's more fun. Tabular is true when each entry in the data, whether or not the top level is object or array, has the same schema.

Tabular:
[[1,2,3],
 [4,5,6],
 [7,8,9]]

[
 {
   "title":"foo",
   "count":3,
},
 {
   "title":"bar",
   "count":2,
},
]

{
  "first": ["foo", 3],
  "second: ["bar", 2]
}

{
  "first": {
    "title":"foo",
    "count":3
    },
  "second": {
    "title":"bar",
    "count":2
}

This data can be displayed tabularly:

row	title	count
first	foo	3
second	bar	2

{
  "first": {
    "name":"foo",
    "coor": {
        "x": 20,
        "y": 18
     },
    },
  "second": {
    "name":"bar",
    "coor": {
        "x": 100,
        "y": 8
     },
}

This data can be displayed tabularly:

entry	name	coor.x	coor.y
first	foo	20	18
second	bar	100	8

However, until we get good schema detection of objects, we cannot know if for certain if json can be displayed as Tabular

To catch the most used "shapes" of JSON data, however, we can check if the second level of encapsulation for each entry is an array. If they are each an array, we can display the JSON as a table.