add discover feature

### Auto discover position

This is a special feature for finding the Y index of row where you data start. For instance you have this following data :

|---------------|---------------|------|-----|
| Nickname      | jo            |      |     |
| First Name    | John          |      |     |
| Last Name     | Doe           |      |     |
|               |               |      |     |
| Employment    | CEO           |      |     |
| Post          | Doe           |      |     |
|               |               |      |     |
|               | Personal info | Age  | 26  |
|               | Sex           | Male |     |
|               |               |      |     |

You want extract `Employment` information and `Personal info` but we do not know if extra information will not come and break our index. This feature can be useful is this case.

You must change Y position (rows) by the column index and regex, the parser will search on this column the index row of this regex, here our rule :

cell position: [4,1], key: 'employment'

became

cell position: [[0, /Employment/],1], key: 'employment'
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