Add workflow for uploading dev builds of Plotly.js

[emilykl]

Closes #7759

• Add new upload-dev-build.yml workflow which uploads a development build of plotly.js every time a new commit is pushed to a PR
• Builds are uploaded to a private repo and made available via GitHub Pages at the following URLs:
  • https://plotly.github.io/plotly.js-dev-builds/upload/pr-{PR_NUM}/latest/plotly.min.js (for the latest commit on a PR)
  • https://plotly.github.io/plotly.js-dev-builds/upload/pr-{PR_NUM}/{SHA}/plotly.min.js (for a specific commit SHA on a PR)
  • */plotly.js and */plot-schema.json also work
• Also split publish-dist jobs into a separate publish-dist.yml workflow, so that the upload-dev-build workflow can be triggered as soon as publish-dist finishes, without waiting for all the tests to complete

Steps for testing

• Note: The workflow_run trigger always runs the version of the workflow on the default branch. This is an important security feature, but it means workflow_run won't allow us to test this implementation
• Instead, manually trigger this workflow using the "Run workflow" button on this page
  • Select Branch: persistent-dev-build-url-2 (this branch)
  • Enter PR number 7795 (this PR) and Run ID 25766159639 (a completed run of the publish-dist workflow for this PR)
• Wait for the run to complete. After it finishes, on the run page you should see an output containing the links. Here's an example from a previous run. It will take about 2-3 minutes for the GitHub Pages deployment to finish before the links become functional.

[emilykl]

@camdecoster FYI there are no major changes to the contents of the publish-dist workflow steps.

[camdecoster]

Suggested change

	name: Upload dev build from PR

[emilykl]

Because of the (silly) way GHA woks, changing this title will break the link between this workflow file and the version on master. I'll update the title immediately before merging.

[emilykl]

have not forgotten about this, I will update before merging

[emilykl]

@camdecoster Following up on one of our previous discussions, GitHub Pages has a total size limit of 1 GB.

That works out to about ~50 separate dev builds (1000 MB / 20 MB = 50). A little lower than I was hoping, but if that turns out not to be enough, we can decrease the retention time and/or save only the latest build for each PR rather than individual copies per commit.

I suppose another option is to retain only plotly.min.js and ditch plotly.js and plot-schema.json.