Compose sequences can end in internal key names

This adds the '\n' and '\t' sequences to showcase the new feature.

srcs/compose/compose/extra.json

@@ -3,5 +3,9 @@
     "s": "Š",
     "c": "Č",
     "z": "Ž"
+  },
+  "\\": {
+    "n": "\\n",
+    "t": "\\t"
   }
 }

srcs/juloo.keyboard2/ComposeKey.java

@@ -42,7 +42,7 @@ public final class ComposeKey
     else if (next_header == 0xFFFF) // String final state
     {
       int next_length = edges[next];
-      return KeyValue.makeStringKey(
+      return KeyValue.getKeyByName(
           new String(states, next + 1, next_length - 1));
     }
     else // Character final state.