Mention icudtl.dat requirement in README.m130.md

Author: HinTak

relnotes/README.m130.md

@@ -16,6 +16,10 @@ Since m128 (last beta release):
     overloaded as an alias to this, too.
 
   * The `SkUnicode` class is now available under python as `skia.Unicode`.
+    The constructor is known to fail on windows - It is likely that downloading
+    a `icudtl.dat` file, renaming from the versioned data-bin-{l,b}.zip in
+    https://github.com/unicode-org/icu/releases, is needed. Windows users please report
+    success/failure on this.
 
   * There are two examples `shape_text.py` (a python port of upstream's example), and
     `skparagraph-example.py` hosted [elsewhere](https://github.com/HinTak/skia-python-examples/).