Use tmxData.type instead of file extension and also return a result for xml extension

[customautosys]

Dear Olivier,

I would like to suggest this change as for those of us using a build step (React / Vue), "tsx" is usually recognised as a typescript-jsx file type which renders us unable to import an asset with that extension as it would be parsed wrongly. Therefore, I suggest to use the type attribute instead of the file extension if available. Also, if the type is XML, it should allow the user to deal with whatever was parsed rather than simply returning nothing.

[obiot]

it could even be simplified to result = data.map || data.tilesets[0];.

after all tsx files only defines tileset, so if map is defined its a tmx file, and if not it's automatically a tsx file.

[customautosys]

I just pushed a new commit customautosys@95eb9b7 but it's not appearing yet, I did result = data.map || data.tilesets[0] || data; so in case for some reason there is no "map" or "tilesets" it'll still return something.