Add worker task to VS Code (#5605)

* add worker task to vscode

* add documentation for devcontainer backgorund workers

* fix misphrased sentence ("want need" -> "need")

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Co-authored-by: Oliver Lippert <oliver@lipperts-web.de>

.vscode/tasks.json

@@ -6,6 +6,12 @@
 
   "version": "2.0.0",
   "tasks": [
+    {
+      "label": "worker",
+      "type": "shell",
+      "command": "inv worker",
+      "problemMatcher": [],
+    },
     {
       "label": "clean-settings",
       "type": "shell",