Added docker shell detection to the login command with instructions on how to use export/import.

Author: bsutton

.devcontainer/Dockerfile

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+# See here for image contents: https://github.com/microsoft/vscode-dev-containers/tree/v0.245.0/containers/ubuntu/.devcontainer/base.Dockerfile
+
+# [Choice] Ubuntu version (use ubuntu-22.04 or ubuntu-18.04 on local arm64/Apple Silicon): ubuntu-22.04, ubuntu-20.04, ubuntu-18.04
+ARG VARIANT="jammy"
+FROM mcr.microsoft.com/vscode/devcontainers/base:0-${VARIANT}
+
+# [Optional] Uncomment this section to install additional OS packages.
+# RUN apt-get update && export DEBIAN_FRONTEND=noninteractive \
+#     && apt-get -y install --no-install-recommends <your-package-list-here>
+
+
+RUN apt update && apt install apt-transport-https
+
+ RUN wget -qO- https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo gpg --dearmor -o /usr/share/keyrings/dart.gpg
+
+ RUN echo 'deb [signed-by=/usr/share/keyrings/dart.gpg arch=amd64] https://storage.googleapis.com/download.dartlang.org/linux/debian stable main' | sudo tee /etc/apt/sources.list.d/dart_stable.list
+
+RUN apt update && apt install dart

.devcontainer/devcontainer.json

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+// For format details, see https://aka.ms/devcontainer.json. For config options, see the README at:
+// https://github.com/microsoft/vscode-dev-containers/tree/v0.245.0/containers/ubuntu
+{
+	"name": "Ubuntu",
+	"build": {
+		"dockerfile": "Dockerfile",
+		// Update 'VARIANT' to pick an Ubuntu version: jammy / ubuntu-22.04, focal / ubuntu-20.04, bionic /ubuntu-18.04
+		// Use ubuntu-22.04 or ubuntu-18.04 on local arm64/Apple Silicon.
+		"args": { "VARIANT": "ubuntu-22.04" }
+	},
+
+	// Use 'forwardPorts' to make a list of ports inside the container available locally.
+	// "forwardPorts": [],
+
+	// Use 'postCreateCommand' to run commands after the container is created.
+	// "postCreateCommand": "uname -a",
+
+	// Comment out to connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.
+	"remoteUser": "vscode",
+	"features": {
+		"git": "latest",
+		"github-cli": "latest"
+	}
+}