docs: CHARTS-8818 add rendering spec documentation (#86)

Author: mongo-J

README.md

@@ -29,6 +29,7 @@ yarn add @mongodb-js/charts-embed-dom
 - [Installation & MongoDB Docs](https://docs.mongodb.com/charts/master/embedding-charts-sdk/)
 - [Embedding SDK API Reference](https://www.npmjs.com/package/@mongodb-js/charts-embed-dom)
 - [Examples](https://github.com/mongodb-js/charts-embed-sdk/tree/master/examples)
+- [Embedded Chart Rendering Specification](https://github.com/mongodb-js/charts-embed-sdk/tree/master/docs/rendering-spec.md)
 
 ### Embedded Chart Guides
 
@@ -47,4 +48,4 @@ yarn add @mongodb-js/charts-embed-dom
 - [Dashboard embedding with custom JWT authentication](https://github.com/mongodb-js/charts-embed-sdk/tree/master/examples/dashboard/authenticated-custom-jwt)
 - [Dashboard embedding with App Services authentication via Realm Web SDK](https://github.com/mongodb-js/charts-embed-sdk/tree/master/examples/dashboard/authenticated-realm-web)
 - [Dashboard embedding with Google authentication](https://github.com/mongodb-js/charts-embed-sdk/tree/master/examples/dashboard/authenticated-google)
-- [Accessing a Chart instance via Dashboard class](https://github.com/mongodb-js/charts-embed-sdk/tree/master/examples/dashboard/unauthenticated-get-chart)
+- [Accessing a Chart instance via Dashboard class](https://github.com/mongodb-js/charts-embed-sdk/tree/master/examples/dashboard/unauthenticated-get-chart)