Support Multi-Source Vector Tile

[Kanahiro]

This plugin needs two .jsons, tiles.json and style.json.
one tiles.json means one source, and only one tiles.json can be set as tile provider on this plugin.
This means, the plugin don't support multi-source vector tile.

I guess two ways to support them.

1:style.json only loading
Now this plugin don't allow to load vector tiles by only style.json. Always needs tiles.json, but style.json includes link to a couple of tiles.json and therefore, you should be able to load tiles by only style.json (like Mapbox GL JS).

2:styling layers of only one source
When style.json has multi-source, no layers will be styled on this plugin.
Maybe only layers set as tiles.json can be styled on even multi-source style.json.

Please advise me.