Use ResizeObserver for responsive charts

[Lexachoc]

Original discussion: plotly/react-plotly.js#380
Related PR: plotly/react-plotly.js#379

This is a follow-up to #2974.

Based on plotly/react-plotly.js#380 (comment), I'm opening this PR in plotly.js as well so config.responsive can use ResizeObserver directly.

[Lexachoc]

I also want to confirm this description; it seems this option still exists in v4:

plotly.js/src/plot_api/plot_config.js

Lines 127 to 134 in acddada

	responsive: {
	valType: 'boolean',
	dflt: false,
	description: [
	'Determines whether to change the layout size when window is resized.',
	'In v3, this option will be removed and will always be true.'
	].join(' ')
	},

[Lexachoc]

There is one failed check:

@flaky should only transition the layout when both traces and layout have animatable changes by default

I'm not sure whether this is related to my changes. If it is, how should I address it, or can it be ignored?