Add devcontainer

.devcontainer/Dockerfile

@@ -0,0 +1,9 @@
+# See here for image contents: https://github.com/microsoft/vscode-dev-containers/tree/v0.163.1/containers/alpine/.devcontainer/base.Dockerfile
+
+# [Choice] Alpine version: 3.13, 3.12, 3.11, 3.10
+ARG VARIANT="3.13"
+FROM mcr.microsoft.com/vscode/devcontainers/base:0-alpine-${VARIANT}
+
+# ** [Optional] Uncomment this section to install additional packages. **
+RUN apk update \
+     && apk add --no-cache shellcheck

.devcontainer/devcontainer.json

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+{
+  "name": "Alpine",
+  "build": {
+    "dockerfile": "Dockerfile",
+    "args": { "VARIANT": "3.13" }
+  },
+  "settings": {
+    "terminal.integrated.shell.linux": "/bin/ash",
+    "shellcheck.enable": true,
+    "shellcheck.enableQuickFix": true,
+    "shellcheck.run": "onType",
+    "editor.formatOnSave": true
+  },
+  "extensions": ["timonwong.shellcheck", "esbenp.prettier-vscode"],
+  "remoteUser": "vscode"
+}