Should update pyright

[wch]

The version of pyright that is used in shinylive is based on a fork from Microbit, and it is getting somewhat out of date and contains a few bugs that have been fixed in more recent versions of pyright.

It would be good to replace the Microbit build of pyright with one based on the main branch of pyright. Some useful information here:

microsoft/pyright#3222
https://github.com/microbit-foundation/pyright/blob/microbit/THIS_FORK.md

[wch]

Done in #138.