feat: context object for onFinish to allow more control for developers

[JamesLMilner]

Description of Changes

Adds context object to onFinish event to provide more context to how the finish event happened. This means you should be able to do this going forward:

draw.on("finish", (id: string, context: { action: string, mode: string }) => {
  if (action === 'draw') {
    // Do something for draw finish event
  } else if (action === 'dragFeature') {
    // Do something for a drag finish event
  } else if (action === 'dragCoordinate') {
    //
  }else if (action === 'dragCoordinateResize') {
    //
  }
});

Link to Issue

#253

PR Checklist

• There is a associated GitHub issue
• If I have added significant code changes, there are relevant tests
• If there are behaviour changes these are documented