Show the server's version history in the About popup

The About popup is twice as wide and shows the player's and the server's
version history side by side, each in its own scrolling column. The
server's comes from GET /api/v1/version/history every time the popup
opens. The description, which is about both, is centred above the
columns, and each history starts right under its version.

main/MainWindow.tscn

@@ -78,9 +78,9 @@ offset_bottom = 860.0
 unique_name_in_owner = true
 visible = false
 layout_mode = 1
-offset_left = 720.0
+offset_left = 360.0
 offset_top = 153.0
-offset_right = 720.0
+offset_right = 360.0
 offset_bottom = 153.0
 
 [node name="LogPopup" parent="." unique_id=1289881388 instance=ExtResource("14_26rwn")]