add devcontainer configuration

.devcontainer/Dockerfile

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+FROM debian:bullseye
+
+LABEL version="0.1"
+LABEL maintainer="[email protected]"
+LABEL description="sotmjp2022 build environment"
+
+RUN apt-get -y update && apt-get -y full-upgrade && \
+    apt-get -y --no-install-recommends install locales sudo build-essential git lv ruby ruby-dev bundler zlib1g-dev && \
+    apt-get -y autoremove && apt-get -y clean && rm -rf /var/lib/apt/lists/*
+
+ARG UID=1000
+ARG GID=1000
+ARG USER_LOCALE=ja_JP.UTF-8
+ARG GEM=/usr/local/gem
+
+RUN sed -i -e "s/^# \(${USER_LOCALE}\)/\1/g" /etc/locale.gen && \
+    echo "LANG=${USER_LOCALE}" > /etc/default/locale && \
+    dpkg-reconfigure --frontend=noninteractive locales && \
+    update-locale LANG=${USER_LOCALE} && \
+    groupadd -g ${GID} docker && \
+    useradd -u ${UID} -g ${GID} -s /bin/bash -m docker && \
+    gpasswd -a docker docker && \
+    mkdir -p ${GEM} && \
+    chown ${UID}:${GID} ${GEM}
+
+ENV LANG ${USER_LOCALE}
+ENV LANGUAGE ja
+ENV GEM_HOME ${GEM}
+
+USER ${UID}

.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/v0.245.2/containers/docker-existing-dockerfile
+{
+	"name": "sotmjp2022",
+	"build": {
+		// Update the 'dockerFile' property if you aren't using the standard 'Dockerfile' filename.
+		"dockerfile": "Dockerfile",
+		// Sets the run context to one level up instead of the .devcontainer folder.
+		"context": ".."
+	},
+	"customizations": {
+		"vscode": {
+			"extensions": [
+				"ms-vscode.live-server",
+				"michelemelluso.code-beautifier",
+				"ecmel.vscode-html-css",
+				"kargware.vscode-extension-jekyll-kw",
+				"wingrunr21.vscode-ruby",
+				"davidanson.vscode-markdownlint"
+			]
+		}
+	},
+
+	// Use 'forwardPorts' to make a list of ports inside the container available locally.
+	"forwardPorts": [4000],
+
+	// Uncomment the next line to run commands after the container is created - for example installing curl.
+	// "postCreateCommand": "apt-get update && apt-get install -y curl",
+	"postCreateCommand": "export PATH=$PATH:/usr/local/gem && gem update && bundle install",
+
+	// Uncomment when using a ptrace-based debugger like C++, Go, and Rust
+	// "runArgs": [ "--cap-add=SYS_PTRACE", "--security-opt", "seccomp=unconfined" ],
+
+	// Uncomment to use the Docker CLI from inside the container. See https://aka.ms/vscode-remote/samples/docker-from-docker.
+	// "mounts": [ "source=/var/run/docker.sock,target=/var/run/docker.sock,type=bind" ],
+
+	// Uncomment to connect as a non-root user if you've added one. See https://aka.ms/vscode-remote/containers/non-root.
+	"remoteUser": "docker"
+}

README.md

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+# State of the map Japan 2022 Website
+
+## How to preview website with Docker and Visual studio code
+
+1. Install [Docker Desktop](https://www.docker.com/) or Docker CLI and [Visual studio code](https://code.visualstudio.com/)
+2. Install the [Remote development extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.vscode-remote-extensionpack) in visual studio code
+3. Open sotmjp2022 directory from visual studio code, and select "Reopen in container" in popup dialog
+   * Other way: Open sotmjp2022 directory and click the Remote window button on the Remote status bar, then select "Reopen in container"
+4. Wait a moment for the build environment to be set up in docker
+5. Open "new terminal" in visual studio code and enter the following command
+
+```bash
+bundle exec jekyll serve
+```