New Concept: 3rd party integrations

We now have a completely new page called integrations.
It allows you to connect Postiz with external services to: Generate video/pictures, send webhooks, etc.
The first integration is up: HeyGen - you can convert your post into a video of you talking! pretty neat :)
If you have a SaaS, feel free to add it as an integration.
Docs will be uploaded soon!

What's Changed

• Add Integrations by @nevo-david in #833
  Full Changelog: v1.53.0...v1.54.0