Capitalize the first letter of custom keys

This is more useful than turning the entire string full caps.

srcs/juloo.keyboard2/KeyModifier.java

@@ -122,7 +122,8 @@ class KeyModifier
           c = Character.toUpperCase(kc);
         return (kc == c) ? k : k.withChar(c);
       case String:
-        return KeyValue.makeStringKey(k.getString().toUpperCase(), k.getFlags());
+        String s = Utils.capitalize_string(k.getString());
+        return KeyValue.makeStringKey(s, k.getFlags());
       default: return k;
     }
   }

srcs/juloo.keyboard2/StringUtils.java

@@ -0,0 +1,12 @@
+package juloo.keyboard2;
+
+final class Utils
+{
+  /** Turn the first letter of a string uppercase. */
+  public static String capitalize_string(String s)
+  {
+    // Make sure not to cut a code point in half
+    int i = s.offsetByCodePoints(0, 1);
+    return s.substring(0, i).toUpperCase() + s.substring(i);
+  }
+}