docs(gen): add codespaces configuration MTA-4778 (#3549)

* docs(gen): add codespaces configuration MTA-4778

* docs(gen): add info file

Author: SamyOubouaziz

.devcontainer/devcontainer.json

@@ -0,0 +1,7 @@
+{
+  "customizations": {
+    "vscode": {
+      "extensions": ["unifiedjs.vscode-mdx"]
+    }
+  }
+}

.devcontainer/info.md

@@ -0,0 +1,23 @@
+# Devcontainer, the Gihub Codespaces configuration file
+
+This configuration is intended for [Github Codespaces](https://docs.github.com/en/codespaces) users.
+
+The `devcontainer.json` file allows to specify a configuration that can be used to create a Codespace.
+
+Refer to the official [Codespaces devcontainers documentation](https://docs.github.com/en/codespaces/setting-up-your-project-for-codespaces/adding-a-dev-container-configuration) for more information.
+
+## Elements
+
+The code below forces the installation of the MDX extension for VSCode inside a Codespace.
+
+    ```json
+    {
+      "customizations": {
+        "vscode": {
+          "extensions": ["unifiedjs.vscode-mdx"]
+        }
+      }
+    }
+    ```
+
+**Note:** The identifier of the extension (e.g. `unifiedjs.vscode-mdx`) can be found on the VSCode extension page, under "More info".