Include the gitlens extension in CCFs devcontainer (#4665)

.devcontainer/devcontainer.json

@@ -5,7 +5,8 @@
   "extensions": [
     "ms-vscode.cpptools",
     "ms-python.python",
-    "esbenp.prettier-vscode"
+    "esbenp.prettier-vscode",
+    "eamodio.gitlens"
   ],
   "settings": {
     "editor.defaultFormatter": "esbenp.prettier-vscode",