add revision index to app revisions table (#3413)

Co-authored-by: David Townley <davidtownley@Davids-MacBook-Air.local>

internal/models/app_revision.go

@@ -26,4 +26,7 @@ type AppRevision struct {
 
 	// PorterAppID is the ID of the PorterApp that the revision belongs to.
 	PorterAppID int `json:"porter_app_id"`
+
+	// RevisionNumber is the number of the revision respective to that porter_app_id and deployment_target_id
+	RevisionNumber int `json:"revision_number"`
 }