docs(readme): Adds docs for creating the repo facades.

Author: ryasmi

readme.md

@@ -3,8 +3,15 @@
 
 ### Usage
 1. Install it with `npm i @js-migrations/core`.
+1. [Create a repository facade](#create-a-repository-facade)
 1. [Use the factory to create the service facade](#use-the-factory).
 
+### Create a repository facade
+This package contains the [RepoFacade TypeScript interface](./src/RepoFacade.ts). You can create a facade to match the interface using the factories below.
+
+- [Knex](https://github.com/js-migrations/knex)
+- [Mongo](https://github.com/js-migrations/mongo) - Coming Soon.
+
 ### Use the factory
 ```typescript
 import migrationsServiceFactory from '@js-migrations/core/dist/factory';