[FEAT] Introduce a plugin to expose the bpmn-visualization "style API" with names as parameters

[tbouffard]

Rationale

See #73

Proposal

• plugin class: StyleByNamePlugin (find a better name)
• plugin id: style-by-name
• methods: all "style" related methods from BpmnElementsRegistry

Example of usage

const stylePlugin =  bpmnVisualization.getPlugin<StyleByNamePlugin>(‘style-by-name’);
stylePlugin.updateStyle('activity-name-1', {...})