update JupyterLab homepage URL (#3785)

- ref. https://github.com/awesome-selfhosted/awesome-selfhosted/issues/3558
- https://jupyterlab.github.io/jupyterlab/ : HTTP 404

README.md

@@ -1814,7 +1814,7 @@ _Related: [Software Development - Low Code](#software-development---low-code)_
 - [HttPlaceholder](https://github.com/dukeofharen/httplaceholder) - Quickly mock away any webservice using HttPlaceholder. HttPlaceholder lets you specify what the request should look like and what response needs to be returned. `MIT` `C#`
 - [ICEcoder](https://icecoder.net/) - ICEcoder is a web IDE / browser based code editor, which allows you to develop websites directly within the web browser. ([Demo](http://demo.icecoder.net/ICEcoder/), [Source Code](https://github.com/icecoder/ICEcoder)) `MIT` `PHP`
 - [Judge0 CE](https://judge0.com) - Open source API to compile and run source code. ([Source Code](https://github.com/judge0/judge0)) `GPL-3.0` `Ruby`
-- [JupyterLab](https://jupyterlab.github.io/jupyterlab/) - Web-based environment for interactive and reproducible computing. ([Demo](https://mybinder.org/v2/gh/jupyterlab/jupyterlab-demo/try.jupyter.org?urlpath=lab), [Source Code](https://github.com/jupyterlab/jupyterlab/)) `BSD-3-Clause` `Python/Docker`
+- [JupyterLab](https://jupyterlab.readthedocs.io/en/stable/) - Web-based environment for interactive and reproducible computing. ([Demo](https://mybinder.org/v2/gh/jupyterlab/jupyterlab-demo/try.jupyter.org?urlpath=lab), [Source Code](https://github.com/jupyterlab/jupyterlab/)) `BSD-3-Clause` `Python/Docker`
 - [Lowdefy](https://www.lowdefy.com/) - Build internal tools, BI dashboards, admin panels, CRUD apps and workflows in minutes using YAML / JSON on an self-hosted, open-source platform. Connect to your data sources, host via Serverless, Netlify or Docker. ([Source Code](https://github.com/lowdefy/lowdefy)) `Apache-2.0` `Nodejs`
 - [ML Workspace](https://github.com/ml-tooling/ml-workspace) - All-in-one web-based IDE for machine learning and data science. `Apache-2.0` `Docker`
 - [RStudio Server](https://www.rstudio.com/products/rstudio/#Server) - Web browser based IDE for R. ([Source Code](https://github.com/rstudio/rstudio)) `AGPL-3.0` `Java/C++`