[ADD] social marketing: added social marketing documentation to v14

[ksc-odoo]

Task ID: 2850055

[robodoo]

Pull request status dashboard.

[ksc-odoo]

Hi @mivu-odoo

here's the social marketing doc for v14. If you could please review it at your earliest convenience, that would be greatly appreciated.

Once you approve, I'll be sure to send it along to Zac for further technical review.

Thanks!

[mivu-odoo]

As of commit 991c8dc

Fixed the build errors! This PR passes all the code checks now.

• Removed unexpected indent in create_posts.rst
• Fixed file path reference in campaigns.rst and push_notifications.rst, it was referencing a file called manage_social but that file didn't exist when I searched the repo. I'm guessing that was the old name for create_posts.rst so I updated the file path references to create_posts