Pytorch advanced examples

[Simone-Bordoni]

Add examples in pytorch as requested in #1423

Checklist:

• [ ] Reviewers confirm new code works as expected.
• [ ] Tests are passing.
• [ ] Coverage does not decrease.
• [ ] Documentation is updated.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 97.11%. Comparing base (1b6eb8a) to head (4837b6a).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1427 +/- ## ======================================= Coverage 97.11% 97.11% ======================================= Files 81 81 Lines 11679 11680 +1 ======================================= + Hits 11342 11343 +1 Misses 337 337 ``` | [Flag](https://app.codecov.io/gh/qiboteam/qibo/pull/1427/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/qiboteam/qibo/pull/1427/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | `97.11% <100.00%> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam#carryforward-flags-in-the-pull-request-comment) to find out more.

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[Simone-Bordoni]

@BrunoLiegiBastonLiegi working at this example I found the problem of the weights not updating... I will address it in a new PR in order to make this example work