Follow up tasks for new Cognee Integration

[julian-risch]

As a follow up to the merged PR #2979 that added a cognee-haystack integration, we need to add an integration page in https://github.com/deepset-ai/haystack-integrations, documentation pages in https://github.com/deepset-ai/haystack, and a social media announcement.

Checklist

Ensure the following checklist is complete before closing this issue.

Tasks

• The code is documented with docstrings and was merged in the main branch
• Docs are published at https://docs.haystack.deepset.ai/
• There is a Github workflow running the tests for the integration nightly and at every PR
• A new label named like integration:<your integration name> has been added to the list of labels for this repository
• The labeler.yml file has been updated
• The package has been released on PyPI
• An integration tile with a usage example has been added to https://github.com/deepset-ai/haystack-integrations
• The integration has been listed in the Inventory section of this repo README
• The feature was announced through social media