Allow configuration of horizontal legend max height (ratio || pixel)

[p1-ra]

Currently, horizontal legend max height is hardcode to 50% of the full layout height. It's not possible to configure an other behaviour.

plotly.js/src/components/legend/draw.js

Lines 607 to 610 in 4ac68aa

	opts._maxHeight = Math.max(
	(isBelowPlotArea || isAbovePlotArea) ? fullLayout.height / 2 : gs.h,
	30
	);

This PR introduce two new legend properties to allow customization the max height ratio or directly the max height in pixel

  hmaxheightratio: {
        valType: 'number',
        min: 2,
        dflt: 2,
        role: 'style',
        editType: 'legend',
        description: [
	    'Sets the max height ratio (layout / ratio) of the visible legend when horizontaly aligned.',
	    'Default value is 2; the legend will take up to 50% of the layout height before displaying a scrollbar',
	].join(' ')
    },
    hmaxheight: {
        valType: 'number',
        min: 0,
        role: 'style',
        editType: 'legend',
        description: 'Sets the max height (in px) of the horizontaly aligned legend.'
    },

[archmoj]

@p1-ra thanks very much for the PR.
Maybe by inverting the hmaxheightratio: we could combine the two attributes into one.
Something like:

maxheight: {
    valType: 'number',
    min: 0,
    dflt: 0.5,
    role: 'style',
    editType: 'legend',
    description: [
      'If greater than one, it sets the max height (in px) of the horizontaly aligned legend.',
      'Otherwise, it sets the max height ratio (layout * ratio) of the visible legend when horizontaly aligned.',
      'Default value is 0.5; the legend will take up to 50% of the layout height before displaying a scrollbar'
    ].join(' ')
},

[nicolaskruchten]

A small update on timing: our team is working hard on releasing v2.0 of Plotly.js, which we anticipate will happen in early April. This PR would be a good candidate to land in the library in v2.1 or later, so with apologies for the delay, we will likely not be able to give much feedback on this PR for the next few weeks :)

[gvwilson]

This pull request has been sitting for a while, so I would like to close it as part of our effort to tidy up our public repositories. I've assigned it to myself to keep track of it; I'll wait until 2024-06-17 for someone to say it's still relevant and they'll to take it on, and otherwise I will close it then. Thanks - @gvwilson