vscode: add programs.vscode.argv option

[Vortriz]

Description

I am currently on Niri WM and require to setup a keyring to be used with vscode. For that I need to write to .vscode/argv.json. There seems to be no HM option for this yet.

For now, I have added it manually, but it would be nice to have an option.

PS: The file already contains some important information, so it should not be completely overwritten, rather append to.