Add changelog; fix two minor blib2to3 issues

CHANGES.md

@@ -6,6 +6,8 @@
 
 - Warn about Python 2 deprecation in more cases by improving Python 2 only syntax
   detection (#2592)
+- Add partial support for the match statement. As it's experimental, it's only enabled
+  when `--target-version py310` is explicitly specified (#2586)
 
 ## 21.10b0
 

src/blib2to3/pygram.py

@@ -96,6 +96,7 @@ class _python_symbols(Symbols):
     or_test: int
     parameters: int
     pass_stmt: int
+    pattern: int
     patterns: int
     power: int
     print_stmt: int
@@ -153,6 +154,7 @@ class _pattern_symbols(Symbols):
 python_grammar_no_print_statement_no_exec_statement_async_keywords: Grammar
 python_grammar_no_exec_statement: Grammar
 pattern_grammar: Grammar
+python_grammar_soft_keywords: Grammar
 
 python_symbols: _python_symbols
 pattern_symbols: _pattern_symbols