Support multiple level headers

[thuydx55]

Consider you have a table like below:

┌─────┬────────────────────────────────────────────────────┬───────────────────────────────────────────────┐
│ No. │                 Person Information                 │            Credit Card Information            │
│     ├───────────┬─────┬────────────┬──────────┬──────────┼────────────┬───────────────┬──────────────────┤
│     │   Name    │ Age │     City   │  State   │ Zip Code │  Card Type │ Last 4 Digits │ Expiration Date  │
├─────┼───────────┼─────┼────────────┼──────────┼──────────┼────────────┼───────────────┼──────────────────┤
│  1  │ John Doe  │  21 │ Vienna     │ Virginia │   22349  │ VISA       │      1234     │     Jan─21       │
│  2  │ Jane Doe  │  28 │ Greenbelt  │ Maryland │   20993  │ MasterCard │      2345     │     Jun─22       │
│  3  │ Paul Ryan │  19 │ Alexandria │ Virginia │   22312  │ JCB        │      4567     │     Oct─24       │
└─────┴───────────┴─────┴────────────┴──────────┴──────────┴────────────┴───────────────┴──────────────────┘

This PR handle multi-level headers and map to object in the same structure.

Tests added.

[ozlerhakan]

Hi @thuydx55 ,

Thank you for the chances!

Do we need to add new feature section on the readme file? you may update https://github.com/ozlerhakan/poiji#feature-6 instead, wdyt?

[thuydx55]

@ozlerhakan Agreed with you. I've just updated README, merged my example to feature 6.

[ozlerhakan]

great! this will be in 3.0.2 :)

[ozlerhakan]

merged! @thuydx55