docs: add examples for basic root fields

Author: avbentem

examples/flask_sqlalchemy/README.md

@@ -53,6 +53,11 @@ and run some queries!
     __typename
   }
 
+  employee(id: "RW1wbG95ZWU6Mw==") {
+    name
+    hiredOn
+  }
+
   allEmployees(sort: [HIRED_ON_ASC, NAME_ASC], first: 2) {
     edges {
       cursor

examples/flask_sqlalchemy/schema.py

@@ -51,6 +51,11 @@ class Query(graphene.ObjectType):
     # Expose `node` root field as mandated by Relay specification
     node = relay.Node.Field()
 
+    # Basic root fields, e.g. `employee(id: "RW1wbG95ZWU6Mw==")`
+    employee = relay.Node.Field(Employee)
+    role = relay.Node.Field(Role)
+    department = relay.Node.Field(Department)
+
     # Allow sorting over one or multiple columns, by default over the primary
     # key, e.g. `allEmployees(sort: [HIRED_ON_ASC, NAME_ASC, ID_ASC])`; not
     # specifying `sort` is the same as using `sort=Employee.sort_argument()`