Add lsp-pyright-library-folders-fn for workspace library folders

[Hxppdv]

Avoid importing project root when temporarily viewing files outside the workspace.

[wyuenho]

What should probably be done is to add an :activation-fn to the client definition to look up a pyrightconfig.json file or a pyproject.toml with a tool.pyright section, and turn off multiroot so lsp-pyright isn't activated on every python mode buffer.