[Feature] Backlinking Usages in Queries / Mutations / Other types from a Type

[aryascripts]

Backlinking

This is a feature that exists in other documentation (not GraphQL), and it super important for discoverability. The way this feature really works is that on each GraphQL "Type", you see where this type is used, and can be queried from. For example, if we have the following types:

type Order {
  id: ID!
  products: [Product!]
}

type ShoppingCart {
  id: ID!
  products: [Product!]
}

type Product {
  id: ID!
  name: String!
}

And when we look at the "Product" type, it should let me know at the bottom of the type, that you can query this type from the other two fields.
An example generated text/markdown for the schema above would be:

SAMPLE HTML/MARKDOWN BELOW

Product

A singular product that is available

Fields

• id: ID! (Identity field of the particular product)
• name: String! (Name of the particular product)

Usages <-- This is the new feature

• Field products in type ShoppingCart (link)
• Field products in type Order (link)

[newhouse]

partial duplicate of #398

[newhouse]

I like this in general. Just need to find the time to implement new features and nice-to-haves. Right now I'm focusing mainly on bugs until I get a bit more free time to devote.