PostHog driver
v2 (#18) * cleanup, php8 types, upgraded deps, first stab at posthog driver * driver created callback * no default value, some backends do better without it * posthog test * list PH up front * ci * ci * .
v2 (#18) * cleanup, php8 types, upgraded deps, first stab at posthog driver * driver created callback * no default value, some backends do better without it * posthog test * list PH up front * ci * ci * .