Add stagger map support

[darkautism]

Support staggered map.
See #403

[rparrett]

Thanks.

I won't be able to take a close look for a few days, but just a few thoughts from a quick skim:

• Ideally, we should depend on a tiled from crates.io. If a release isn't imminent, we can wait or do a separate PR without stagger support.
• We should turn off compression for the example tilemap so its data is readable.
• I think the even / odd problem must be on our side.
• Is the file not found error from BytesResourceReader user-facing at all? I could see users potentially being confused when their files exist, but we are emitting this error because we just can't support loading sub-resources or whatever.

[darkautism]

Is the file not found error from BytesResourceReader user-facing at all?

I think user will not fact file not found error because I only use this loader load a tmx. If a tmx use extern png it will load behind.
But i'm not sure TSX tileset. rs-tiled has some tileset's attribute bug so it cannot read tsx correctly.

[StarArawn]

I believe this is because of how bevy handles Y coordinates. In tiled map editor Y down goes into the positive and in bevy Y down goes into the negative. When we load the tiles in we end up flipping the entire tilemap along the Y axis using: mapped_y = tiled_map.map.height - 1 - y;. Because of this we also need to "flip" the stagger.

[rparrett]

That makes sense. I'm not sure what to do about that other than add a comment to explain the situation.