Add JupyterLab language servers for Bash, Markdown, and YAML.

Need to configure the environment to support [language servers](https://jupyterlab-lsp.readthedocs.io/en/latest/Language%20Servers.html) for Bash, Markdown, and YAML. This should be easy but for some reason, I can't get JupyterLab to detect the language servers on launch.

