Please read the documentation. These are "web version" examples. They use our spine-ts runtime and backends, like spine-webgl, spine-canvas, etc. However, for the "web version" examples to work, the code of the runtimes needs to be compiled to .js files, like the spine-webgl.js file your browser complains about. For that compilation to happen, you need to compile them, which is done via npm run dev.
