Add dialyzer dependency

Add typespecs to several functions

lib/matrix_server_web/client/request/create_room.ex

@@ -5,6 +5,16 @@ defmodule MatrixServerWeb.Client.Request.CreateRoom do
 
   alias Ecto.Changeset
 
+  @type t :: %__MODULE__{
+    visibility: String.t(),
+    room_alias_name: String.t(),
+    name: String.t(),
+    topic: String.t(),
+    invite: list(String.t()),
+    room_version: String.t(),
+    preset: String.t()
+  }
+
   @primary_key false
   embedded_schema do
     field :visibility, :string