ForceGenerate parameter to @goModel added.

[atzedus]

When using autobind directive in configuration, there is no chance to force gqlgen to generate a model if that name matched with model from the autobind package. One solution is rename the type name in graphql schema, but it is not an ideal way.
This PR solves this problem. For example if your package is defined in configuration like:

autobind:
  - myproject/entity

And it have type, for example: Person.

type Person {
  name: String
}

then it will autobind to myproject/entity.Person

If you need to exclude this model from autobind, you can define it like:

type Person @goModel(forceGenerate: true) {
  name: String
}

I have:

• Updated any relevant documentation (see docs)