fix(canvas): [PKG-CANVAS-04] preserve public type and export compatibility

refactor/fixtures/consumers/canvas-published.ts

@@ -0,0 +1,11 @@
+import Artplayer from 'artplayer'
+import canvas from 'artplayer-proxy-canvas'
+
+const callback = (context: CanvasRenderingContext2D, video: HTMLVideoElement) => context.drawImage(video, 0, 0)
+const art = new Artplayer({ container: '#player', url: 'video.mp4', proxy: canvas(callback) })
+const result = canvas(callback)(art)
+const actual: HTMLCanvasElement = result
+const context: CanvasRenderingContext2D | null = result.getContext('2d')
+const accepted: Parameters<typeof canvas>[0] = callback
+const originalResult: ReturnType<ReturnType<typeof canvas>> = document.createElement('canvas')
+void [actual, context, accepted, originalResult]