fix(dia.Paper)!: fix `paper:pinch` dispatched event type

[kumilingus]

Description

For consistency, all events fired on paper are passed native events wrapped in the mvc.$.Event wrapper.

Before:

paper.on('paper:pinch', (evt) => console.log('this is a native event', evt));

Now:

paper.on('paper:pinch', (evt) => console.log('this is a native event', evt.originalEvent));