Visual Studio Code: Set Workspace recommended extensions (#1398)

Codify the Recommended VS Code Extensions:

- [Shell Syntax](https://marketplace.visualstudio.com/items?itemName=bmalehorn.shell-syntax)
- [ShellCheck](https://marketplace.visualstudio.com/items?itemName=timonwong.shellcheck)
- [Shell Format](https://marketplace.visualstudio.com/items?itemName=foxundermoon.shell-format)

Documentation: https://code.visualstudio.com/docs/editor/extension-marketplace#_workspace-recommended-extensions

Author: andygrunwald

.vscode/extensions.json

@@ -0,0 +1,8 @@
+{
+  "recommendations": [
+    "bmalehorn.shell-syntax",
+    "timonwong.shellcheck",
+    "foxundermoon.shell-format"
+  ],
+  "unwantedRecommendations": []
+}