Smoother Beeminder Trend Lines

[dreeves]

### Desiderata
- [x] Add screenshots
- [x] Have someone read a draft
- [ ] Keywords/tags
- [x] Title image
- [ ] Link preview excerpt
- [x] Publish at https://blog.beeminder.com/smooth on 2022-12-02
- [x] Blog blurbs [either done or too late]
- [x] NIX: Waggledance [too late]
- [ ] Tweet
- [x] NIX: Tip of the day
- [x] New gissue for death to the rosy line: https://github.com/beeminder/road/issues/268

Guest post by Uluc.

Verbata: nerds, technical, uluc saranli, beebrain, graph aesthetics, smoove b love man, nerdery, math, data smoothing,

[dreeves]