Re-implement Gosling API functions in `v2`

[sehilyi]

API functions are entirely unimplemented in the v2 branch. An example function is zoomTo, which navigates to a specific genomic range from the JS side. It looks like implementing the missing API functions seems to be the main thing left for releasing v2.

The complete list of API functions defined in v1 can be found in createApi().

gosling.js/src/api/api.ts

Line 48 in b7f7f0a

export function createApi(

The API functions need to be implemented in this new createAPIV2() function:

gosling.js/src/api/api.ts

Lines 53 to 59 in 4133f37

	// TODO: After fully implementing this, remove `Partial` from the return type
	export function createApiV2(): Pick<GoslingApi, 'subscribe' | 'unsubscribe'> & Partial<GoslingApi> {
	return {
	subscribe,
	unsubscribe
	};
	}

API Functions to Implement

Subscribing Events

• subscribe
• unsubscribe

Exporting Images

• getCanvas
• exportPng
• exportPdf

Zoom (#1165)

• zoomTo
• zoomToExtent
• zoomToGene
• suggestGene

Retrieving Track/View Information

• getTrackIds
• getTracksAndViews
• getTracks
• getTrack
• getViews
• getView