Initialize module and dependencies

vendor/github.com/emersion/go-imap/v2/thread.go

@@ -0,0 +1,9 @@
+package imap
+
+// ThreadAlgorithm is a threading algorithm.
+type ThreadAlgorithm string
+
+const (
+	ThreadOrderedSubject ThreadAlgorithm = "ORDEREDSUBJECT"
+	ThreadReferences     ThreadAlgorithm = "REFERENCES"
+)