I checked and it looks like widget-ts-cookiecutter readme already removed the JupyterLab part of instructions leaving just pip install ...
I did the same in my repo but the widget-svelte-cookiecutter that I used still has it.
I already have one active pull request open there. I’ll see if I can figure out how to send a separate one concerning install instructions).
Huge thanks to @cabreraalex for sharing the Svelte widget template Creating Modern, Reactive Jupyter Widgets with Svelte
I found it through Svelte channels and it totally made my day 