ICU-5801 Merging the last update in readme.html from maint-3-8, which added the warning note about ICU4J charset converter implementation issues.

X-SVN-Rev: 22683
diff --git a/readme.html b/readme.html
index 2a8deea..285f644 100644
--- a/readme.html
+++ b/readme.html
@@ -151,6 +151,11 @@
 usage. For more information, see <a href="">
 Formatting Dates and Times</a> in the User Guide.
+<p><b>Status of ICU4J charset converter</b>
+<p>The ICU4J implementation of java.nio.charset.Charset is included as a Technology
+Preview. Not all functionality from the java.nio.Charset interfaces is operational,
+and some converters are known to mis-handle Unicode supplementary characters. Use with caution.
 <p><b>New features</b>
 See the <a href="">ICU 3.8 download page</a> about new features in this release.