style-guide.md: add tip to view file locally (#1928)

contributing-guides/style-guide.md

@@ -33,6 +33,12 @@ tldrl -f {{page.md}}
 For other ways to use `tldrl`, such as linting an entire directory, check out (what else!)
 [`tldr tldrl`](https://github.com/tldr-pages/tldr/blob/master/pages/common/tldrl.md)
 
+If you're using the Node.js client of `tldr`, you can preview a page locally using the `-f` flag (aka `--render`):
+
+```
+tldr -f {{page.md}}
+```
+
 ## Token syntax
 
 User-provided values should use the `{{token}}` syntax