Add .vscode profile for easier contributions (#536)

### Description of the change

This adds a `.vscode` folder with recommended extensions and some useful settings like unittest schema validation.
The `.vscode` folder is already helm ignored during packaging.

### Possible drawbacks

We would have to be careful about PR changes in that directory.

Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/536
Co-authored-by: justusbunsi <sk.bunsenbrenner@gmail.com>
Co-committed-by: justusbunsi <sk.bunsenbrenner@gmail.com>

.vscode/extensions.json

@@ -0,0 +1,8 @@
+{
+    "recommendations": [
+        "yzhang.markdown-all-in-one",
+        "DavidAnson.vscode-markdownlint",
+        "Tim-Koehler.helm-intellisense",
+        "esbenp.prettier-vscode"
+    ]
+  }