Enable link opening

[dbirks]

I've found that installing xdg-utils is the missing piece to get vscode to be able to open links in devcontainers.

One of the things it installs is open. Tested that it triggers the browser to open:

open https://nasa.gov

I've used that for other cli tools in the past that try to open the browser nicely, but I haven't tried it with sfdx personally. I assume it's using the same method to open things.

And I'm using that apt-packages feature instead of apt install xdg-utils just because it's pre-built and a little easier to consume.

[dbirks]

Ah looks like I'll need someone else to merge: