Support configuring default runtime

[Reidond]

I don't have nodejs install on windows (I only use WSL2 and this extension doesn't work in wsl2 for some reason).

So I quickly installed bun and unfortunatelly extension tries to install tsx using npm, which I don't have because no node. So I simply install it via bun install.

I could possibly alias node to bun, but it would be cool to also have setting in vs code. Thx ❤️