chore: add .devcontainer config (#2700)

Co-authored-by: Tony Brix <tony@brix.ninja>
Closes https://github.com/markedjs/marked/issues/2699

.devcontainer/devcontainer.json

@@ -0,0 +1,18 @@
+// For format details, see https://aka.ms/devcontainer.json. For config options, see the
+// README at: https://github.com/devcontainers/templates/tree/main/src/javascript-node
+{
+	"name": "marked",
+	// We're using node 14 for development, to keep close to the engine compatibility that marked.js uses.
+	"image": "mcr.microsoft.com/devcontainers/javascript-node:0-14",
+	"postCreateCommand": "npm install",
+
+	// Configure tool-specific properties.
+	"customizations": {
+		// Configure properties specific to VS Code.
+		"vscode": {
+			"extensions": [
+				"dbaeumeur.vscode-eslint"
+			]
+		}
+	}
+}