Add .devcontainer configuration (#10114)

.devcontainer/Dockerfile

@@ -0,0 +1,24 @@
+#-------------------------------------------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See https://go.microsoft.com/fwlink/?linkid=2090316 for license information.
+#-------------------------------------------------------------------------------------------------------------
+
+FROM mcr.microsoft.com/dotnet/core/sdk:3.0.100-preview6
+
+# Avoid warnings by switching to noninteractive
+ENV DEBIAN_FRONTEND=noninteractive
+
+# Configure apt and install packages
+RUN apt-get update \
+    && apt-get -y install --no-install-recommends apt-utils 2>&1 \
+    #
+    # Verify git, process tools, lsb-release (common in install instructions for CLIs) installed
+    && apt-get -y install git procps lsb-release \
+    #
+    # Clean up
+    && apt-get autoremove -y \
+    && apt-get clean -y \
+    && rm -rf /var/lib/apt/lists/*
+
+# Switch back to dialog for any ad-hoc use of apt-get
+ENV DEBIAN_FRONTEND=dialog

.devcontainer/devcontainer.json

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+// See https://aka.ms/vscode-remote/devcontainer.json for format details.
+{
+	"name": ".NET Core 3.0-preview6, including pwsh (Debian 10)",
+	"dockerFile": "Dockerfile",
+
+	// Uncomment the next line to run commands after the container is created.
+	"postCreateCommand": "cd src/powershell-unix && dotnet restore",
+
+	"extensions": [
+		"ms-azure-devops.azure-pipelines",
+		"ms-vscode.csharp",
+		"ms-vscode.powershell",
+		"DavidAnson.vscode-markdownlint",
+		"vitaliymaz.vscode-svg-previewer"
+	]
+}