chore: add Posthog to playground for tracking and survey usage

[perkinsjr]

What does this PR do?

Fixes # (issue)

If there is not an issue for this, please create one first. This is used to tracking purposes and also helps use understand why this PR exists

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] Chore (refactoring code, technical debt, workflow improvements)
• [ ] Enhancement (small improvements)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How should this be tested?

• Test A
• Test B

Checklist

Required

• [ ] Filled out the "How to test" section in this PR
• [ ] Read Contributing Guide
• [ ] Self-reviewed my own code
• [ ] Commented on my code in hard-to-understand areas
• [ ] Ran pnpm build
• [ ] Ran pnpm fmt
• [ ] Checked for warnings, there are none
• [ ] Removed all console.logs
• [ ] Merged the latest changes from main onto my branch with git pull origin main
• [ ] My changes don't cause any responsiveness issues

Appreciated

• [ ] If a UI change was made: Added a screen recording or screenshots to this PR
• [ ] Updated the Unkey Docs if changes were necessary

_{Huly®: ENG-1766}

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Latest commit: 1c8891a047bd631f8e57950d9e96db13c1a8c716

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