feat: new label module

Takes a text label, with the ability to include embedded scripts.

Resolves #80.

examples/config.corn

@@ -67,6 +67,8 @@ let {
 
     $clipboard = { type = "clipboard" max_items = 3 truncate.mode = "end" truncate.length = 50 }
 
+    $label = { type = "label" label = "random num: {{500:echo $RANDOM}}" }
+
     // -- begin custom --
     $button = { type = "button" name="power-btn" label = "" on_click = "popup:toggle" }
 
@@ -97,7 +99,7 @@ let {
     }
     // -- end custom --
 
-    $left = [ $workspaces $launcher ]
+    $left = [ $workspaces $launcher $label ]
     $right = [ $mpd_local $mpd_server $phone_battery $sys_info $clipboard $power_menu $clock ]
 }
 in {