feat: add link to song on Apple Music

Didn't consider this before as it would be nicer to link to somewhere
that shows my music history, but this is likely the best option
available for now.

server/src/scrapers/apple_music.rs

···
     album_name: String,
     artist_name: String,
     artwork: AppleMusicTrackArtwork,
+    url: String,
 }
 
 #[derive(Deserialize, Debug, Clone)]
···
             name: track.attributes.name.clone(),
             image: artwork_url,
             context,
-            url: None,
+            url: Some(track.attributes.url.clone()),
         })
     }
 

server/src/templates/index.rs

···
             name: "We Might Feel Unsound".to_owned(),
             image: "https://is1-ssl.mzstatic.com/image/thumb/Music124/v4/f4/b2/8e/f4b28ee4-01c6-232c-56a7-b97fd5b0e0ae/00602527857671.rgb.jpg/240x240bb.jpg".to_owned(),
             context: "James Blake — James Blake".to_owned(),
-            url: None
+            url: Some("https://music.apple.com/gb/album/we-might-feel-unsound/1443124478?i=1443125024".to_owned())
         })),
     ]
 }