Show notification if there are projects that haven't been added to the workspace (#14046)

* add check for if there are projects that haven't been added to the workspace

* add check when workspace folders change

* add comment

* update wording

* filter for multiple file extensions at the same time

* add test

* addressing comments

extensions/data-workspace/package.json

@@ -34,6 +34,11 @@
           "projects.defaultProjectSaveLocation": {
             "type": "string",
             "description": "%projects.defaultProjectSaveLocation%"
+          },
+          "projects.showNotAddedProjectsInWorkspacePrompt": {
+            "type": "boolean",
+            "description": "%projects.showNotAddedProjectsInWorkspacePrompt%",
+            "default": true
           }
         }
       }
@@ -153,6 +158,7 @@
     ]
   },
   "dependencies": {
+    "fast-glob": "^3.1.0",
     "@microsoft/ads-extension-telemetry": "^1.1.1",
     "vscode-nls": "^4.0.0"
   },