Enable 'Equal Earth' projection

[apparebit]

Equal Earth is an aesthetically pleasing, fairly recent equal-area pseudocylindrical projection, which has has been adopted by the NASA Goddard Institute for Space Studies. I am submitting this pull request after @alexcjohnson encouraged me to do so in the plotly forum.

[alexcjohnson]

Thanks @apparebit ! This looks great, I'll defer to @archmoj (who's on vacation this week) for whether this needs to be included in a test image or a Jasmine test - anyway we'll wait to merge until he's back.

@archmoj the webgl-jasmine tests were particularly flaky here, took 3 retries before they passed. Is this just a bad day at CircleCI or has that test gotten flakier recently?

[archmoj]

Thanks very much for the PR.

Please add examples of using this new projection in the following mocks:

1. test/image/mocks/various_geo_projections.json
2. test/image/mocks/geo_fitbounds-locations.json
3. test/image/mocks/canada_geo_projections.json

Then you could collect & commit new baselines from the ARTIFACTS tab of test-baselines on CircleCi.

[apparebit]

I think I have the mock JSON files figured out by now. I am not a fan of having to manually shift most of the map cells by one position nor of the mocks using Albers USA as a kind of sentinel (surprise!). Having said that, the robotically incrementing numbers mod 8 is long done. I just need CircleCI to provide me with the updated and correct images. After that, the PR should be ready.

Alas, the "webgl-jasmine" tests are incredibly flaky but I cannot do reruns. Even after signing up with CircleCI with my GitHub account, it insists that I need write permissions to the project. Two options:

1 . You can empower me and I'll persist with reruns until the board is green.
2. I have to rely on one of you to do this in my stead.

This is obviously your call. Either works for me. Thank you

[archmoj]

New baselines are now available at https://output.circle-artifacts.com/output/job/86068e44-8fa5-4ad9-837a-c78716ce6d35/artifacts/0/baselines.tar (or from https://app.circleci.com/pipelines/github/plotly/plotly.js/8921/workflows/5a975e79-dec3-47df-84d2-e0a0d010bcda/jobs/196144/artifacts in case you don't want to unzip them).
Please update those at test/image/baselines.
Thank you!

[apparebit]

@archmoj, I think I was committing them while you were writing the comment. The versions I pushed to the branch show Equal Earth and properly shift all subsequent cells including the Albers sentinel.

[archmoj]

Fantastic. 🎖️ 🏆 💃