Ensure trailing slash, if str does not end with slash, it will be added
确保后缀，如果字符串不以斜杠结尾，则将添加斜杠
ensureTrailingSlash('/foo/bar') // => /foo/bar/ Copy
ensureTrailingSlash('/foo/bar') // => /foo/bar/
Ensure trailing slash, if str does not end with slash, it will be added
确保后缀，如果字符串不以斜杠结尾，则将添加斜杠