Update release notes for NaBL2.

source/release/note/vnext.rst

@@ -16,6 +16,15 @@ Stratego has two new reserved words: ``cast`` and ``is``. Local variables can be
 
 Under the Stratego language options in your ``metaborg.yaml`` file you can turn on the gradual type system, if you use the incremental compiler. This option is ``gradual: static``, and only tests the types statically. The default is ``gradual: none`` right now, meaning the gradual type system is not on by default. There is an experimental third option ``gradual: dynamic`` which not only checks the types statically but also inserts casts to check types dynamically where necessary.
 
+NaBL2
+~~~~~
+
+NaBL2 supports a new resolution algorithm based on fexid-point environment computation instead of graph search, which can be enabled by adding ``strategy environments`` to the ``name-resolution`` signature section.
+It has much better performance characteristics, especially when dealing with mutually importing scopes and transitive imports.
+Compared the the search-based, the environment-based algorithm can get stuck on scope graphs with cycles involving scopes importing references that can be resolved via that same scope.
+Note that the environment-based algorithm may increase memory usage.
+The default remains the search-based algorithm.
+
 Eclipse
 ~~~~~~~