Add devcontainer.json configuration

Author: ark120202

.devcontainer/devcontainer.json

@@ -0,0 +1,9 @@
+{
+    "name": "TypeScriptToLua.github.io",
+    "image": "mcr.microsoft.com/vscode/devcontainers/javascript-node:14",
+    "settings": {
+        "terminal.integrated.shell.linux": "/bin/bash"
+    },
+    "extensions": ["dbaeumer.vscode-eslint", "editorconfig.editorconfig", "esbenp.prettier-vscode"],
+    "postCreateCommand": "npm ci"
+}