Create a python file should automatically select the language for the file as python

[karthiknadig]

Testing #18355

Currently create a python file opens a generic untitled file. Instead, it should set the language on the untitled file.

[luabud]

@karthiknadig Do you know if there's a command to do it? Cause AFAIK it can't be done programmatically :(

[karthiknadig]

We should ask for this API in VS Code repo. There is a command 'Change language mode', but this does a quick pick.

[luabud]

I guess they do offer a way through this? https://code.visualstudio.com/updates/v1_59#_contribution-point-for-new-file-menu