Snippet editor can't parse nest snippet correctly.

[zjffun]

For example this snippet:

{
    "test-snippets-container": {
        "test-snippet": {
            "prefix": "test-snippet",
            "description": "test-snippet",
            "scope": "",
            "body": [
                "test-snippet"
            ]
        }
    }
}

VS Code support this format, but not mentioned in the documentation. See: https://github.com/microsoft/vscode/blob/ecf479e662923a158c04ab58a835549a312442bf/src/vs/workbench/contrib/snippets/browser/snippetsFile.ts#L242-L248