[Feature Request] Add post published fixed to username_feed

[rafaelribeiroo]

Before submitting an issue, make sure you have:

• [x] Updated to the lastest version v1.6.0
• [x] Read the README and docs
• [x] Searched the bugtracker for similar issues including closed ones
• [x] Reviewed the sample code in tests and examples

Which client are you using?

• [x] app (instagram_private_api/)
• [ ] web (instagram_web_api/)

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Describe your Feature Request:

I would like to see in username_feed function, the key to check if post_published_fixed is true or false