schema link added to docs toc. (#734)

Author: kidunot89

docs/toc.md

@@ -24,3 +24,7 @@
 - [Using Composite Product Data + Mutations](using-composite-product-data-and-mutations.md)
 - [Using Product Bundle Data + Mutations](using-product-bundle-data-and-mutations.md)
 - [Using Product Add-ons Data + Mutations](using-product-addons-data-and-mutations.md)
+
+## Other
+
+- [Schema Docs](https://woographql.com/schema)