"Inspect Data" (ALT - D) should work on textures

[emackey]

Currently it works on "images", but not "textures". We should look up the image associated with a texture.

Might also be good for it to work on texture sources inside materials, if possible.

[emackey]

Come to think of it, "Go to Definition" could actually open an image, for PNGs and JPGs at least, instead of running the image viewer webview, if that helps streamline the behavior of peek etc. "Inspect" would be different from "Go to" then.

On the language server definition provider side, this would mean returning a location that pointed at the image's actual file URI, rather than returning the internal gltf-dataUri reference. Would the behavior be better? This wouldn't work for KTX2, though.