Add support for dot accessors to be numbers

This is an interesting special case in the old parser where numbers
are allowed as dot accessors, but they are specifically convertred
to being an item accessor during the parsing phase. We now support
numbers being parsed for dot accessors in the new parser.

grammar.ebnf

@@ -233,7 +233,7 @@ variable_accessor_call
 variable_accessor_dot
     =
     accessor_type:`dot`
-    "." parameter:IDENTIFIER
+    "." parameter:( IDENTIFIER | NUMBER_LITERAL )
     ;
 
 variable_accessor_call_parameters

src/jinja2/new_parser.py

@@ -801,8 +801,12 @@ def parse_variable_accessor(node, ast):
         accessor_node = nodes.Getitem()
         accessor_node.arg = parse_variable(ast['parameter'])
     elif accessor_type == 'dot':
-        accessor_node = nodes.Getattr()
-        accessor_node.attr = ast['parameter']
+        if isinstance(ast['parameter'], str):
+            accessor_node = nodes.Getattr()
+            accessor_node.attr = ast['parameter']
+        else:
+            accessor_node = nodes.Getitem()
+            accessor_node.arg = parse_literal(ast['parameter'])
     elif accessor_type == 'call':
         accessor_node = parse_variable_accessor_call(ast)