bit.ly/learn-xls and bit.ly/xls-playground should be served from the canonical github repo

[proppy]

currently it's a weird mix of:

• colab saved on gist.github.com
• bootleg wheel downloaded https://github.com/proppy/xls/releases

instead it should be served from https://github.com/google/xls using colab github integration and tested w/ GitHub workflows (similar to what's being done w/ https://github.com/chipsalliance/silicon-notebooks/tree/main/.github/workflows