test(builds): add test build options to github-release tool

This will allow me to run test builds against experimental branches of
the build-emacs-for-macos build script, and publish them under a
pre-release "Test Builds" GitHub Release, rather than a normal nightly
release.

cmd/github-release/plan.go

@@ -6,11 +6,20 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
+type ReleaseType string
+
+type Release struct {
+	Name  string `yaml:"name"`
+	Title string `yaml:"title,omitempty"`
+	Draft bool   `yaml:"draft,omitempty"`
+	Pre   bool   `yaml:"prerelease,omitempty"`
+}
+
 type Plan struct {
-	Commit  *Commit `yaml:"commit"`
-	OS      *OSInfo `yaml:"os"`
-	Release string  `yaml:"release"`
-	Archive string  `yaml:"archive"`
+	Commit  *Commit  `yaml:"commit"`
+	OS      *OSInfo  `yaml:"os"`
+	Release *Release `yaml:"release"`
+	Archive string   `yaml:"archive"`
 }
 
 func LoadPlan(filename string) (*Plan, error) {