[flame_tiled] add availability to loading TiledMap directly

[Hwan-seok]

What could be improved

Change _loadMap to public and create new method static Future<RenderableTiledMap> fromMap(TiledMap map, Vector2 destTileSize)

flame/packages/flame_tiled/lib/src/renderable_tile_map.dart

Line 106 in cae8c0c

final map = await _loadMap(contents);

Why should this be improved

Currently, there are only fromFile and fromString methods for making RenderableTileMap and cannot make TiledMap directly.
The fromString uses _loadMap to loading TiledMap and loads the image directly at the next line.
As a result, there is no chance of retrieving and manipulating the map's image path before the image is actually loaded.

flame/packages/flame_tiled/lib/src/renderable_tile_map.dart

Line 108 in cae8c0c

_renderableTileLayers(map).map((e) => _loadImages(map)),

Imagine that we want to get images from a remote URL.
But _loadImages loads SpriteBatch directly before we know the path of the imageSets of TileMap.
So we cannot inject the image files from a remote URL before flame loads it from local assets.

Any risks?

Misusing of loadMap..? but this isn't very common.

More information

Are you interested in working on a PR for this? YES

It is a long way to go to acheving dynamically fetching maps.. I think this one is starting.

[spydon]

Sounds like a good addition to me, I'll assign you to the issue.