Clarify support for Java 13

nakamura-to · nakamura-to · commit cf1d1ab12cbd · 2019-12-29T09:04:32.000+09:00
diff --git a/README.md b/README.md
@@ -77,6 +77,7 @@ Major versions
 | Java 10 |        |   v    |
 | Java 11 |        |   v    |
 | Java 12 |        |   v    |
+| Java 13 |        |   v    |
 
 License
 -------
