docs: add basedpyright to alternative extensions list (#1833)

docs/extensions-compatibility.md

@@ -26,3 +26,4 @@ The following extensions are functional replacements for incompatible extensions
 
 - [Open Remote - SSH](https://open-vsx.org/extension/jeanp413/open-remote-ssh)
 - [Open Remote - WSL](https://open-vsx.org/extension/jeanp413/open-remote-wsl)
+- [BasedPyright](https://open-vsx.org/extension/detachhead/basedpyright) (open-source alternative to Pylance)