Better posthog-foss syncing

[ungless]

Changes

• this is FAR better way of syncing posthog/posthog with posthog/posthog-foss.
• this happens on push to master, unlike the previous approach which ran on cron

Needed for merge

• Remove SYNC_GITHUB_TOKEN from posthog/posthog-foss
• Add SYNC_GITHUB_TOKEN secret to posthog/posthog
• Disable all actions in https://github.com/posthog/posthog-foss

[ungless]

NB: check is failing due to missing secrets.

[timgl]

I don't think this action should happen on push on every branch, but just on master right? I've added the secret to this repo

[Twixes]

Should now work that way @timgl.

[timgl]

@ungless Ready to merge? Not sure how to test this but might not really matter

[ungless]

All OK as long as all actions are disabled in https://github.com/posthog/posthog-foss -- otherwise actions from this repo will trigger in posthog-foss when pushed.

[Twixes]

I'll merge this in and we'll see how it works.

[Twixes]

Works nicely! @ungless