STRUCTURE: Restructure the Platform docs

[mtrunkat]

• Improve the "Security" section
  • Add email to report vulnerabilities
  • Mention secret environment variables and secret input
• Review the "Limits" section
  • Possibly mention naming limits (63 chars)
  • Reflect the change in limits that will propagate to the new pricing
  • Mention the limits section in the console
• Merge "Introduction" and "Home"
• Create "Publication and monetization" section under "Actors" merging "Paid actors" and "Publishing your actor"
• Rewrite "Access rights" section into "Collaboration" with nested "Organizations" and "Access rights"
• Review the "Schedules" section

[mtrunkat]

Here is a list of redirects that needs to be added for all 3 PRs:

RESTRUCTURE: https://github.com/apify/apify-docs/pull/532

/platform/tutorials/building-public-actors   ->   /platform/actors/publishing
/platform/actors/paid-actors                 ->   /platform/actors/running/actors-in-store#paid-actors
/platform/actors/tasks                       ->   /platform/actors/running/tasks
/platform/actors/running/compute-units       ->   /platform/actors/running/usage-and-resources#cpu
/platform/actors/running/memory-and-cpu      ->   /platform/actors/running/usage-and-resources#memory
/platform/actors/running/input               ->   /platform/actors/running/input-and-output#input
/platform/actors/security                    ->   /platform/security
/platform/actors/limits                      ->   /platform/limits

HOMES: https://github.com/apify/apify-docs/pull/542

/platform/about                                           ->  /platform
/platform/tutorials/quick-startt#run-an-actor             ->  /platform/actors/running
                                #create-an-actor          ->  /platform/actors/development
/platform/tutorials/run-actor-and-retrieve-data-via-api   ->  /academy/api/run-actor-and-retrieve-data-via-api


ACCESS RIGHTS: https://github.com/apify/apify-docs/pull/543

/platform/access-rights                         ->  /platform/collaboration/access-rights
/access-rights/organization-account/            ->  /platform/collaboration/organization-account
/access-rights/organization-account/setup       ->  /platform/collaboration/organization-account/setup
/access-rights/organization-account/how-to-use  ->  /platform/collaboration/organization-account/how-to-use
/access-rights/list-of-permissions              ->   /platform/collaboration/list-of-permissions