VSCode: added devcontainer configuration

.devcontainer/Dockerfile

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+FROM ubuntu:20.04
+
+RUN apt-get update && \
+  apt-get install -y software-properties-common curl && \
+  apt-get upgrade -y
+RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 15CF4D18AF4F7421
+RUN add-apt-repository -yn 'deb http://archive.ubuntu.com/ubuntu/ trusty main' && \
+  add-apt-repository -yn 'deb http://archive.ubuntu.com/ubuntu/ trusty universe' && \
+  add-apt-repository -yn 'deb http://archive.ubuntu.com/ubuntu/ xenial main' && \
+  add-apt-repository -yn 'deb http://archive.ubuntu.com/ubuntu/ xenial universe' && \
+  add-apt-repository -yn 'deb http://archive.ubuntu.com/ubuntu/ bionic main' && \
+  add-apt-repository -yn 'deb http://archive.ubuntu.com/ubuntu/ bionic universe' && \
+  add-apt-repository -yn 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-6.0 main' && \
+  add-apt-repository -yn 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-7 main' && \
+  add-apt-repository -yn 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-8 main' && \
+  add-apt-repository -yn 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-9 main'
+
+RUN apt-get update && apt-get -y install \
+  cmake \
+  ninja-build \
+  git \
+  clang-format \
+  g++-4.4 \
+  g++-4.6 \
+  g++-4.7 \
+  g++-4.8 \
+  g++-4.9 \
+  g++-5 \
+  g++-7 \
+  g++-8 \
+  g++-9 \
+  g++-10 \
+  clang-3.5 \
+  clang-3.6 \
+  clang-3.7 \
+  clang-3.8 \
+  clang-3.9 \
+  clang-6.0 \
+  clang-7 \
+  clang-8 \
+  clang-9 \
+  clang-10 \
+  clang-11

.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/v0.183.0/containers/ubuntu
+{
+  "name": "Ubuntu",
+  "build": {
+    "dockerfile": "Dockerfile"
+  },
+
+  // Set *default* container specific settings.json values on container create.
+  "settings": {},
+
+  // Add the IDs of extensions you want installed when the container is created.
+  "extensions": [
+	"ms-vscode.cmake-tools",
+	"ms-vscode.cpptools"
+],
+
+  // 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",
+}