Add Icicle Trace to Plotly.py

[Kully]

Code PR

• I have read through the contributing notes and understand the structure of the package. In particular, if my PR modifies code of plotly.graph_objects, my modifications concern the codegen files and not generated files.
• I have added tests (if submitting a new feature or correcting a bug) or
  modified existing tests.
• For a new feature, I have added documentation examples in an existing or
  new tutorial notebook (please see the doc checklist as well).
• I have added a CHANGELOG entry if fixing/changing/adding anything substantial.
• For a new feature or a change in behaviour, I have updated the relevant docstrings in the code to describe the feature or behaviour (please see the doc checklist as well).

Other changes in this PR

• Correct setup.py by changing publish to publish-dist. See this line
• Correct the path to plotly express in contributing.md

[nicolaskruchten]

Thanks! This is the right first commit to get this into the library, but I likely won't want to merge this PR alone: I would recommend that you build the PX support and docs into this PR, and I'll rebase and merge on top of master once Plotly.js 2.0 is released and Plotly.py is upgraded to use it.

[Kully]

I would recommend that you build the PX support and docs into this PR

Sounds good. I am currently working on some basic docs right now.

[nicolaskruchten]

Merged via cherry-pick.