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