build: Add VSCode extension recommendations

This commit introduces a `.vscode/extensions.json` file to the project,
which provides recommendations for Visual Studio Code extensions. The
inclusion of this file aims to streamline the development environment
setup for contributors by suggesting a set of useful extensions commonly
employed within the project.

The recommended extensions cover various aspects of development,
including:

* **Code intelligence:**  `npm-intellisense` and `path-intellisense` for
enhanced JavaScript/Node.js and path handling.
* **Documentation:** `jsdoc-generator` for generating JSDoc
documentation, `vscode-markdownlint` for linting Markdown files.
* **Linting and formatting:** `vscode-eslint`, `prettier-vscode`, and
`vscode-stylelint` for enforcing coding style and best practices.
* **HTML/Twig support:** `auto-close-tag`, `auto-rename-tag`, and
`twig-language-2` for better HTML and Twig template development.
* **Markdown assistance:** `markdown-all-in-one` for enhanced Markdown
editing experience.

By including these recommended extensions, contributors can quickly set
up their VS Code environment with relevant tools, leading to a more
productive and consistent coding experience.

.vscode/extensions.json

@@ -0,0 +1,15 @@
+{
+  "recommendations": [
+    "christian-kohler.npm-intellisense",
+    "christian-kohler.path-intellisense",
+    "crystal-spider.jsdoc-generator",
+    "davidanson.vscode-markdownlint",
+    "dbaeumer.vscode-eslint",
+    "esbenp.prettier-vscode",
+    "formulahendry.auto-close-tag",
+    "formulahendry.auto-rename-tag",
+    "mblode.twig-language-2",
+    "stylelint.vscode-stylelint",
+    "yzhang.markdown-all-in-one"
+  ]
+}