Add docker-buildx-plugin for non-moby installation.

[rurabori]

When setup as :

"ghcr.io/devcontainers/features/docker-in-docker:2": {
			"version": "latest",
			"moby": false,
			"dockerDashComposeVersion": "v2",
			"installDockerBuildx": true
		},

Docker complains about missing buildx, adding the plugin install fixes the issue.

[rurabori]

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[samruddhikhandale]

Based on the value for installDockerBuildx option, https://github.com/devcontainers/features/blob/main/src/docker-in-docker/install.sh#L331-L346 should install docker buildx.

The below config works fine for me 👇

{
	"image": "mcr.microsoft.com/devcontainers/base:jammy",
	"features": {
		"ghcr.io/devcontainers/features/docker-in-docker:2": {
			"version": "latest",
			"moby": false,
			"dockerDashComposeVersion": "v2",
			"installDockerBuildx": true
		}
	}
}

@rurabori Is this not working for you? If not, I wonder if you are facing the issue reported in devcontainers/cli#331. If that's the case, do you mind commenting on that issue? Thanks!

[jon-git-king]

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