Change "Read more" URL for custom integrations

[dende]

from "https://docs.crowd.dev/v0/reference/" to "https://crowd.dev/integration-framework"

Changes proposed ✍️

• The old URL contains a versioned link to v0 of the docs which do not contain information about the integration framework.

• Screenshots (front-end changes only)

  - ...
  

Checklist ✅

• Label appropriately with Feature, Enhancement, or Bug.
• Tests are passing.
• New backend functionality has been unit-tested.
• Environment variables have been updated:
  • Local frontend configuration: frontend/.env.dist.local, frontend/.env.dist.composed.
  • Local backend: backend/.env.dist.local, backend/.env.dist.composed.
  • Configuration docs have been updated.
  • Team members only: update environment variables in override, staging and production env. files and trigger update config script.
• API documentation has been updated (if necessary) (see docs on API documentation).
• Quality standards are met.
• All changes have been tested in a staging site.
• All changes are working locally running crowd.dev's Docker local environment.