[analytics] Adding Posthog logs

[LatentDream]

Changes

• Added Posthog logging on Docs

Notes

I've look to modify the build system to inject the key at build time with a env. var., but Jupyter-book is a wrapper for Sphink. It would have been "doable" if we were using Sphink directly, but it doesn't seems possible with jupyter-book alone. I've try some work around, and I couldn't figure out a way.

• Not worth using Shink since everything is done with jupyter-book
• The posthog key is a public key. (Sent to all client. Is written in clear in the html for people to see)
• The key for Google analytics (equivalent to the Posthog) key is also written in clear in this repo. I guess it's because of the same reason.

---

Close #274

---

📚 Documentation preview 📚: https://ploomber-doc--275.org.readthedocs.build/en/275/