feat(MapboxCluster): add props to customize ids

[tmlmt]

Linked issue

Closes #104

Description

• Add two new props to MapboxCluster in order to override the default naming of id:
  • idPrefix to override the default mb-cluster-${index} incremental prefix
  • divId to override the default mb-cluster-${index} incremental encapsulating <div> id
• Updates doc accordingly. I chose to demo those new props in the middle example, MapboxClusterWithPopupDemo, to demonstrate the fact that this cluster gets its customized ids while the one before and after are set with mb-cluster-1 and mb-cluster-2

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[tmlmt]

Hey @titouanmathis, could you have a look at this and consider adding it to the next release? Thanks !

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