Operator node should have `.value`

[bartveneman]

Found while converting css-design-tokens: node.value on an Operator node was null/undefined, had to resort to node.name. https://ast-explorer.dev/#eNolzEEKxCAMheGrhKxmwF7AuYobq6HISCIxrkrv3tDu3g+P78SOEcucGHC8y5TIq3hlOBMDwJ7L/1BZXLciXTRCb0xZt0NzbcT2MQGTEUCpBtj7ou8v8ZXYIXHoYRIOmc2a8EwYwXSRf/C6Af03K48=