add center topic node.

lichao

2021-05-20 0e31f38fc37216e1376d8101d1bcf7a3779279dc

 .vscode/settings.json

@@ -61,7 +61,16 @@
        "strstream": "cpp",
        "unordered_set": "cpp",
        "cfenv": "cpp",
        "*.ipp": "cpp"
        "*.ipp": "cpp",
        "cassert": "cpp",
        "cerrno": "cpp",
        "cfloat": "cpp",
        "ciso646": "cpp",
        "climits": "cpp",
        "ios": "cpp",
        "locale": "cpp",
        "queue": "cpp",
        "random": "cpp"
    },
    "files.exclude": {
        "**/*.un~": true,