Try PostHog alongside Cloudflare on the website #93

Run PostHog next to Cloudflare Web Analytics for a while, to see which one is worth keeping. PostHog uses memory persistence, so it stays cookie-free and the site needs no banner. A deploy of main now also fails when either counter's variable is missing or malformed, or when a page didn't get its counter.

• Try PostHog alongside Cloudflare, and check both before deploying leanmeancleanapps.github.io#24
• Set the POSTHOG_KEY variable (and POSTHOG_HOST outside the US cloud)
• Pick one and remove the other