Allow custom legendNode for markers

[Bigood]

Allow legendNode props on markers for finer control over legend.

Usecases :

• Display other content than text (image, shape…)
• Create tooltips to display additional information, when a lot of markers are rendered and remaining place is low

Usage :

...
markers={[{
    axis: "x",
    lineStyle: {
        stroke: "lightblue",
        strokeWidth: 5
    },
    legendPosition: "top",
    legendNode: <foreignObject x={0} y={0} width={32} height={32}>
                    <FontAwesomeIcon icon={faRocket} />
                </foreignObject>,
}]}

Expected result :

Codechanges :

Two lines changed to bypass legendNode creation with legend text.
Doesn't break any existing functionality, and seams easy to maintain across updates.

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Name	Status	Preview	Comments	Updated (UTC)
nivo	❌ Failed (Inspect)			Sep 20, 2023 3:06pm

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[Bigood]

@plouc Can I do something to help this PR be merged ?

[Nikholau]

lets aprovve this PR @plouc !

[Bigood]

Up'ing this, how can I help?

[plouc]

@Bigood, sorry for the late reply, the PR needs to be rebased, I think it would be good to add a test for it as well, maybe not in the core though, it's probably better to test this on a chart supporting markers.