added csv extension

setup/.vscode/extensions.json

@@ -6,5 +6,6 @@
         "ms-vscode-remote.vscode-remote-extensionpack",
         "yahyabatulu.vscode-markdown-alert",
         "tomoki1207.pdf",
+        "mechatroner.rainbow-csv"
     ]
 }

setup/03_optional-docker-environment/.devcontainer/devcontainer.json

@@ -12,7 +12,8 @@
         "ms-azuretools.vscode-docker",
         "ms-toolsai.jupyter",
         "yahyabatulu.vscode-markdown-alert",
-        "tomoki1207.pdf"
+        "tomoki1207.pdf",
+        "mechatroner.rainbow-csv"
       ]
     }
   }