Embed Notice

For context, here's a quite-meta screenshot of the same feature on #PhanpySocial

Notes:
- Threads has the advantage of doing this in the back-end, so it knows the current index and total count of threads immediately.
- Their UI is smaller, doesn't show the copy 'Thread', probably assuming users automatically understand what the badge means. Not sure why they push the badge at the end of the post sentence.
- They also show the badge on the Post page. #PhanpySocial only show it on the timeline.