Add DevContainer support (#1286)

* Add DevContainer support

* add recommended extension

* cleanup docker file

* Fix json

* Update with new template (from .Net Core 3.0 but adapted for 3.1 and trimmed out unnecessary things)

Author: bergmeister

.devcontainer/Dockerfile

@@ -0,0 +1,31 @@
+#-------------------------------------------------------------------------------------------------------------
+# 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:3.1
+
+# This Dockerfile adds a non-root user with sudo access. Use the "remoteUser"
+# property in devcontainer.json to use it. On Linux, the container user's GID/UIDs
+# will be updated to match your local UID/GID (when using the dockerFile property).
+# See https://aka.ms/vscode-remote/containers/non-root-user for details.
+
+# 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 dialog 2>&1 \
+    #
+    # Verify git, process tools, lsb-release (common in install instructions for CLIs) installed
+    && apt-get -y install git iproute2 procps apt-transport-https gnupg2 curl lsb-release \
+    #
+    # Clean up
+    && apt-get autoremove -y \
+    && apt-get clean -y \
+    && rm -rf /var/lib/apt/lists/*
+    
+RUN pwsh -c Install-Module platyPS,Pester -Force
+
+# Switch back to dialog for any ad-hoc use of apt-get
+ENV DEBIAN_FRONTEND=dialog

.devcontainer/devcontainer.json

@@ -0,0 +1,14 @@
+// For format details, see https://aka.ms/vscode-remote/devcontainer.json or the definition README at
+// https://github.com/microsoft/vscode-dev-containers/tree/master/containers/dotnetcore-3.0
+{
+	"name": "C# (.NET Core 3.1)",
+	"dockerFile": "Dockerfile",
+	"settings": {
+		"terminal.integrated.shell.linux": "/usr/bin/pwsh"
+	},
+	"postCreateCommand": "dotnet restore",
+	"extensions": [
+		"ms-vscode.csharp",
+		"ms-vscode.powershell"
+	]
+}

.vscode/extensions.json

@@ -3,6 +3,7 @@
     // for the documentation about the extensions.json format
     "recommendations": [
         "ms-vscode.PowerShell",
-        "ms-vscode.csharp"
+        "ms-vscode.csharp",
+        "ms-vscode-remote.remote-containers"
     ]
 }