osbuild2/ostree.preptree: add missing options

Add the missing options for the `org.osbuild.ostree.preptree` stage.

internal/osbuild2/ostree_preptree_stage.go

@@ -1,7 +1,16 @@
 package osbuild2
 
+// Transforms the tree to an ostree layout
+
 type OSTreePrepTreeStageOptions struct {
+	// Array of group names to still keep in /etc/group
 	EtcGroupMembers []string `json:"etc_group_members,omitempty"`
+
+	// Array of arguments passed to dracut
+	InitramfsArgs []string `json:"initramfs-args,omitempty"`
+
+	// Create a regular directory for /tmp
+	TmpIsDir *bool `json:"tmp-is-dir,omitempty"`
 }
 
 func (OSTreePrepTreeStageOptions) isStageOptions() {}