feat(bar): add label prefix config opt

This commit makes the label prefix configurable. Users can select if
they want to show an icon, only text, or both text and an icon.

komorebi-bar/src/config.rs

@@ -164,3 +164,15 @@ impl From<KomorebiTheme> for KomobarTheme {
         }
     }
 }
+
+#[derive(Copy, Clone, Debug, Serialize, Deserialize, JsonSchema)]
+pub enum LabelPrefix {
+    /// Show no prefix
+    None,
+    /// Show an icon
+    Icon,
+    /// Show text
+    Text,
+    /// Show an icon and text
+    IconAndText,
+}