Add Lemmy Icon (#353)

src/icons/icons.yml

@@ -7881,6 +7881,13 @@ icons:
     categories:
       - Brand Icons
 
+  - name:       Lemmy
+    id:         lemmy
+    unicode:    f371
+    created:    1.3
+    url:        join-lemmy.org
+    categories:
+      - Brand Icons