Documentation updates for 5.11

[LiamConnors]

Documentation PR

• I've seen the doc/README.md file
• This change runs in the current version of Plotly on PyPI and targets the doc-prod branch OR it targets the master branch
• If this PR modifies the first example in a page or adds a new one, it is a px example if at all possible
• Every new/modified example has a descriptive title and motivating sentence or paragraph
• Every new/modified example is independently runnable
• Every new/modified example is optimized for short line count and focuses on the Plotly/visualization-related aspects of the example rather than the computation required to produce the data being visualized
• Meaningful/relatable datasets are used for all new examples instead of randomly-generated data where possible
• The random seed is set if using randomly-generated data in new/modified examples
• New/modified remote datasets are loaded from https://plotly.github.io/datasets and added to https://github.com/plotly/datasets
• Large computations are avoided in the new/modified examples in favour of loading remote datasets that represent the output of such computations
• Imports are plotly.graph_objects as go / plotly.express as px / plotly.io as pio
• Data frames are always called df
• fig = <something> call is high up in each new/modified example (either px.<something> or make_subplots or go.Figure)
• Liberal use is made of fig.add_* and fig.update_* rather than go.Figure(data=..., layout=...) in every new/modified example
• Specific adders and updaters like fig.add_shape and fig.update_xaxes are used instead of big fig.update_layout calls in every new/modified example
• fig.show() is at the end of each new/modified example
• plotly.plot() and plotly.iplot() are not used in any new/modified example
• Hex codes for colors are not used in any new/modified example in favour of these nice ones

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).

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[nicolaskruchten]

Hey @LiamConnors, I've just merged your changes from doc-prod into master and also updated Plotly.js to 2.16.1 and approved the Percy snapshots, so if you want to merge the tip of master into this branch you'll have a passing build and an easier time :)

[LiamConnors]

Hey @LiamConnors, I've just merged your changes from doc-prod into master and also updated Plotly.js to 2.16.1 and approved the Percy snapshots, so if you want to merge the tip of master into this branch you'll have a passing build and an easier time :)

Thanks @nicolaskruchten. I've done that now.

[nicolaskruchten]

This is a cool page, thanks for adding it!

Some feedback:

1. Neither plot has a legend, because you're using a single trace with hardcoded colors, so there's no way of knowing what green and blue mean. I would suggest a separate trace per year and then another one for the line but hide the line from the legend.
2. Along similar lines, it might be cool to have a third example (or a modified second example) with some lines that go the other way and that are colored red, say. Again I would make this a different trace so it can have a legend entry.

This is not blocking feedback, just something that's on my mind as I've always wanted a PX function to do this stuff :)