Builds Don't Work with PostCSS After Update

In Node v17:

```Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath './lib/tokenize' is not defined by "exports" in /tmp/workspace/node_modules/postcss-safe-parser/node_modules/postcss/package.json```

In earlier versions of Node, this was just a deprecation warning:

```Update this package.json to use a subpath pattern like "./*".```