Rename Themes module to Theme for consistency

src/QBar/Server.hs

@@ -7,7 +7,7 @@ import QBar.Core
 import QBar.Cli
 import QBar.ControlSocket
 import QBar.Host
-import QBar.Themes
+import QBar.Theme
 
 import Control.Monad (forever, when, unless, forM_)
 import Control.Concurrent.Async

src/QBar/Themes.hs → src/QBar/Theme.hs

-module QBar.Themes where
+module QBar.Theme where
 
 import QBar.BlockOutput