chore: add devcontainer.json for GitHub codespace

.devcontainer/devcontainer.json

@@ -0,0 +1,16 @@
+{
+    "image":"mcr.microsoft.com/devcontainers/cpp:ubuntu-22.04",
+    "features": {
+        "ghcr.io/devcontainers/features/python:1": {},
+        "ghcr.io/devcontainers/features/sshd:1": {}
+    },
+	"postCreateCommand": "sudo sh -ce 'apt update && apt install g++-12 -y && echo export CC=gcc-12 CXX=g++-12 >> /etc/profile.d/set-compiler.sh'",
+	"customizations": {
+		"vscode": {
+			"extensions": [
+				"llvm-vs-code-extensions.vscode-clangd",
+				"DavidAnson.vscode-markdownlint"
+			]
+		}
+	}
+}