Add some basic docs on the new config file

docs/content/config.md

@@ -0,0 +1,38 @@
+---
+linkTitle: Configuration
+title: How to configure gqlgen using gqlgen.yml
+description: How to configure gqlgen using gqlgen.yml
+menu: main
+weight: -7
+---
+
+gqlgen can be configured using a `gqlgen.yml` file, by default it will be loaded from the current directory, or any parent directory.
+
+Example:
+```yml
+schema: schema.graphql
+
+# Let gqlgen know where to put the generated server
+exec:
+  filename: graph/generated/generated.go
+  package: generated
+
+# Let gqlgen know where to the generated models (if any)
+model:
+  filename: models/generated.go
+  package: models
+
+# Tell gqlgen about any existing models you want to reuse for
+# graphql. These normally come from the db or a remote api.
+models:
+  User:
+    model: github.com/my/app/models.User
+  Todo:
+    model: github.com/my/app/models.Todo
+    fields:
+      id:
+        resolver: true # force a resolver to be generated
+```
+
+Everything has defaults, so add things as you need.
+