[docs] Add tutorials section to torch.package docs (#59499)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59499
**Summary**
This commit adds a tutorials section to the torch.package docs.
**Test Plan**
Continuous integration.
<img width="870" alt="Captura de Pantalla 2021-06-04 a la(s) 5 10 31 p m" src="https://user-images.githubusercontent.com/4392003/120874257-b9ced300-c55a-11eb-84dd-721cb7ac73ab.png">
Test Plan: Imported from OSS
Reviewed By: Lilyjjo
Differential Revision: D29050628
Pulled By: SplitInfinity
fbshipit-source-id: c17ab0100a9d63e7af8da7a618143cedbd0a5872
