Clean up example a little (#89)

## Summary:
I realized:
- it's simpler to avoid the usual `cmd` and just put it all in the same
  directory
- we don't need schema.json since GitHub now posts a schema in SDL
  format

## Test plan:
make lint example


Author: benjaminjkraft

Reviewers: dnerdy, StevenACoffman, aberkan, jvoll, mahtabsabet, MiguelCastillo

Required Reviewers: 

Approved By: dnerdy, StevenACoffman

Checks: ✅ Test (1.17), ✅ Test (1.16), ✅ Test (1.15), ✅ Test (1.14), ✅ Lint, ✅ Test (1.17), ✅ Test (1.16), ✅ Test (1.15), ✅ Test (1.14), ✅ Lint

Pull Request URL: https://github.com/Khan/genqlient/pull/89

example/README.md

@@ -6,7 +6,7 @@ Create a [personal access token](https://docs.github.com/en/github/authenticatin
 To run the example:
 
 ```sh
-$ GITHUB_TOKEN=<your token> go run ./cmd/example/main.go <username>
+$ GITHUB_TOKEN=<your token> go run . <username>
 you are Ben Kraft
 csilvers is Craig Silverstein
 ```

example/cmd/example/main.go

@@ -1,9 +0,0 @@
-package main
-
-import (
-	"github.com/Khan/genqlient/example"
-)
-
-func main() {
-	example.Main()
-}

example/generated.go

@@ -1,4 +1,4 @@
-package example
+package main
 
 // Code generated by github.com/Khan/genqlient, DO NOT EDIT.
 

example/genqlient.yaml

@@ -1,10 +1,11 @@
-# These are the defaults, and are just included to be explicit.
-package: example
 schema: schema.graphql
 operations:
 - genqlient.graphql
 generated: generated.go
 
+# needed since it doesn't match the directory name:
+package: main
+
 # We bind github's DateTime scalar type to Go's time.Time (which conveniently
 # already defines MarshalJSON and UnmarshalJSON).  This means genqlient will
 # use time.Time when a query requests a DateTime, and is required for custom

example/main.go

@@ -1,4 +1,4 @@
-package example
+package main
 
 import (
 	"context"
@@ -19,7 +19,7 @@ func (t *authedTransport) RoundTrip(req *http.Request) (*http.Response, error) {
 	return t.wrapped.RoundTrip(req)
 }
 
-func Main() {
+func main() {
 	var err error
 	defer func() {
 		if err != nil {