Change config format to yaml; add replicators

replicator.go

@@ -0,0 +1,18 @@
+package litestream
+
+type Replicator interface {
+}
+
+// FileReplicator is a replicator that replicates a DB to a local file path.
+type FileReplicator struct {
+	db  *DB    // source database
+	dst string // destination path
+}
+
+// NewFileReplicator returns a new instance of FileReplicator.
+func NewFileReplicator(db *DB, dst string) *FileReplicator {
+	return &FileReplicator{
+		db:  db,
+		dst: dst,
+	}
+}