docs: search by id and custom theme support

Author: gabehf

docs/src/content/docs/guides/editing.md

@@ -60,6 +60,8 @@ Once merged, we can see that all of the listen activity for Tsumugu has been asi
 
 ![an activity heatmap showing more listens than were previously there](../../../assets/merged_activity.png)
 
+You can also search for items when merging by their ID using the format `id:1234`.
+
 #### Deleting Items
 
 To delete at item, just click the trash icon, which is the fourth and final icon in the editing options. Doing so will open a confirmation dialogue. Once confirmed, the item you delete, as well as all of its children

docs/src/content/docs/index.mdx

@@ -34,6 +34,6 @@ import { Card, CardGrid } from '@astrojs/starlight/components';
 		Koito automatically fetches data from MusicBrainz and images from Deezer and Cover Art Archive to compliment what is provided by your music server.
 	</Card>
 	<Card title="Themeable" icon="seti:css">
-		Koito ships with twelve different themes, with custom theme options to be added soon™.
+		Koito ships with twelve different themes, now with support for custom themes!
 	</Card>
 </CardGrid>