Added
- Introduce "period" `ticklabelmode` on cartesian date axes [[4993](https://github.com/plotly/plotly.js/pull/4993), [#5055](https://github.com/plotly/plotly.js/pull/5055), [#5060](https://github.com/plotly/plotly.js/pull/5060), [#5065](https://github.com/plotly/plotly.js/pull/5065), [#5088](https://github.com/plotly/plotly.js/pull/5088), [#5089](https://github.com/plotly/plotly.js/pull/5089)],
this feature was anonymously sponsored: thank you to our sponsor!
- Add new formatting options for weeks and quarters [[5026](https://github.com/plotly/plotly.js/pull/5026)],
this feature was anonymously sponsored: thank you to our sponsor!
- Add `source` attribute to `image` traces for fast rendering [[5075](https://github.com/plotly/plotly.js/pull/5075)]
- Add `zsmooth` attribute for discrete `heatmapgl` traces [[4953](https://github.com/plotly/plotly.js/pull/4953)], with thanks to ordiology for the contribution!
- Add horizontal and vertical markers for arrow charts [[5010](https://github.com/plotly/plotly.js/pull/5010)]
- Add touch support to `rangeslider` [[5025](https://github.com/plotly/plotly.js/pull/5025)], with thanks to priyanomi, cristiantx, JasDev42 for their contribution!
Changed
- Improve contribution guide & readme, add code of conduct [[5068](https://github.com/plotly/plotly.js/pull/5068)]
- Bump various dev-dependencies namely bubleify and glslify [[5084](https://github.com/plotly/plotly.js/pull/5084), [#5085](https://github.com/plotly/plotly.js/pull/5085), [#5118](https://github.com/plotly/plotly.js/pull/5118)]
Fixed
- Fix updating `title` and tick labels during transition with react [[5045](https://github.com/plotly/plotly.js/pull/5045)]
- Fix `table` wheel scroll for Firefox [[5051](https://github.com/plotly/plotly.js/pull/5051)], with thanks to ManelBH for the contribution!
- Fix ISO-8601 short time zone format [[5015](https://github.com/plotly/plotly.js/pull/5015)], with thanks to mtgto for the contribution!
- Fix numeric periods on date axes for `bar` with `base` [[5061](https://github.com/plotly/plotly.js/pull/5061)]
- Fix `bar` and `box` widths on categorical axes in "overlay" mode [[5072](https://github.com/plotly/plotly.js/pull/5072)]
- Fix `symbol` numbers in string format [[5073](https://github.com/plotly/plotly.js/pull/5073)]
- Fix gl2d marker sizes [[5093](https://github.com/plotly/plotly.js/pull/5093)]
- Fix default latitude span in `geo` subplots [[5033](https://github.com/plotly/plotly.js/pull/5033)]
- Improve axis tick increment [[5114](https://github.com/plotly/plotly.js/pull/5114)]