[INFRA] Configure a linter

[tbouffard]

We should apply a configuration close or identical to the one used in https://github.com/process-analytics/bpmn-visualization-js
Be aware of process-analytics/bpmn-visualization-js#2742 and process-analytics/bpmn-visualization-js#2771

As a first implementation, we will duplicate the eslint configuration from the bpmn-visualization repository, then we will use a shared configuration when it is available: #27.
Using the same eslint config as this repository will ease the move of code between the 2 repositories, for instance when

• extracting demo code from the lib to the extension
• graduating experimental features to the lib