curds: Make it possible to cast nodes into a string

We'll use this do display the node in the UI. I add a newline so we
don't have to implement some kind of spacer class.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

curds/playlist/node.py

@@ -23,6 +23,9 @@ class PlaylistNode:
     def __normalize__(self, name):
         return name.title()
 
+    def __str__(self):
+        return f"<small>\n</small><big>{self.name}</big>"
+
     def append_child(self, child):
         prev = None
         if len(self.children) > 0:

curds/playlist/test_node.py

@@ -14,6 +14,7 @@ class TestPlaylistNode(unittest.TestCase):
         n = node.PlaylistNode("test node", "test-icon")
         self.assertEqual(n.icon, "test-icon")
         self.assertEqual(n.name, "Test Node")
+        self.assertEqual(str(n), "<small>\n</small><big>Test Node</big>")
 
     def test_node_less_than(self):
         a = node.PlaylistNode("a")