jupyter notebook support

[DetachHead]

fixes #173

stuff to address before merging:

• [ ] we need to patch the vscode python plugin to change PYLANCE_EXTENSION_ID to "detachhead.basedpyright". if this is the only change we need to make it would be a pain if we had to fork and publish our own version just for that, maybe there's a way we can hack the official extension at runtime?
• [ ] the vscode python plugin launches the "pylance" language server from the one bundled with the extension (ie. does not respect "basedpyright.importStrategy": "fromEnvironment"). i don't know enough about the development workflow of jupyter notebooks users to know if this is a problem or not. (ie. is type checking notebooks in CI a thing?)
• [ ] add tests if possible

[DetachHead]

after looking at how ruff does it, i decided this approach sucks. instead we should add support for typechecking notebooks in the CLI and add support for them in the LSP itself, rather than trying to do it the pylance way