* Analytics: Add PostHog echo backend
Add PostHog as a supported analytics backend for Grafana's echo service.
Users can configure `posthog_token` and optionally `posthog_host` in the
[analytics] section to forward all echo events to PostHog.
* add eslint ignore comments
* update sample.ini
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Co-authored-by: joshhunt <josh.hunt@grafana.com>
Co-authored-by: Ashley Harrison <ashley.harrison@grafana.com>