feat: integrate Mintlify with Mixpanel analytics

[dangrondahl]

Description

Add Mixpanel analytics tracking to the Mintlify docs site by configuring the
Mixpanel integration in docs.json. Once enabled, Mintlify will automatically
track page views, search queries, feedback submissions, context menu
interactions, and navigation clicks.

Tasks

• Obtain the Mixpanel project token from Mixpanel project settings
• Add the integrations.mixpanel block to docs.json:

  "integrations": {
    "mixpanel": {
      "projectToken": "YOUR_MIXPANEL_PROJECT_TOKEN"
    }
  }

• Verify events appear in the Mixpanel dashboard after deploying

References

• https://www.mintlify.com/docs/integrations/analytics/mixpanel
• https://mixpanel.com/settings/project (project token location)