ICU-21249 add unumberrangeformatter.h to API docs main page
diff --git a/icu4c/source/common/unicode/docmain.h b/icu4c/source/common/unicode/docmain.h
index ccf62d0..b7984ad 100644
--- a/icu4c/source/common/unicode/docmain.h
+++ b/icu4c/source/common/unicode/docmain.h
@@ -149,7 +149,7 @@
  *   </tr>
  *   <tr>
  *     <td>Number Range Formatting<br />(includes currency and unit ranges)</td>
- *     <td>(no C API)</td>
+ *     <td>unumberrangeformatter.h</td>
  *     <td>icu::number::NumberRangeFormatter</td>
  *   </tr>
  *   <tr>