Implement posthog for landing page

[Jonathan-Sendsen]

Posthog is an open-source product analytics tool that allows for easy analysis, testing and data observing

Here is a link to their API docs

Here is a comp analysis created for further context around why posthog is the tool we've selected

Feel free to partner with Jonathan on this task so we can better understand the features and functionalities we can get access to on their free plan as well as the customization if we were to host this ourselves.

[Jonathan-Sendsen]

cc: @abrichr