Add devcontainer for building SK-LSP

[adam-fowler]

• Uses swiftlang/swift:nightly-6.0-jammy as a base image
• Installs sqlite3, libsqlite3-dev, libncurses5-dev and python3.
• Adds build arguments -Xcxx -I/usr/lib/swift -Xcxx -I/usr/lib/swift/Block
• Includes swift extension

[ahoppen]

Thanks for the PR @adam-fowler. There is already a PR up to add a dev container to SourceKit-LSP, let’s iterate on that: #916.

I would appreciate your feedback on that PR. I think the pieces that differ are

• You run apt-get dist-uprgrade. I am curious if that’s a recommended thing to do, I don’t do it on Dockerfiles I run at home. Is there any reason to not stick with the distro that comes with the base swiftlang Docker image?
• You set the following options, I’m not sure if they are necessary?

        "ghcr.io/devcontainers/features/common-utils:2": {
            "installZsh": "false",
            "username": "vscode",
            "userUid": "1000",
            "userGid": "1000",
            "upgradePackages": "false"
        },
        "ghcr.io/devcontainers/features/git:1": {
            "version": "os-provided",
            "ppa": "false"
        },

• You set "seccomp=unconfined". Do you remember what that’s needed for?
• You set "remoteUser": "vscode", is that needed?