Add support for basedpyright

[KotlinIsland]

Name: basedpyright URL: https://github.com/DetachHead/basedpyright

It's like Pyright but much better. ("pyright fork with various type checking improvements")

[GerardoGR]

For me, setting:

let g:python_pyright_executable = 'basedpyright-lamgserver'

did the trick. Not sure if there are other settings needed.