Support namespace selectors

The namespace declarations work as expected but the namespace selectors do not:

@namespace svg url(http://www.w3.org/2000/svg);
@namespace xl "http://www.w3.org/1999/xlink";

svg|a {}

[xl|href] {}

namespace_statement [0, 0] - [0, 47]
  namespace_name [0, 11] - [0, 14]
  call_expression [0, 15] - [0, 46]
    function_name [0, 15] - [0, 18]
    arguments [0, 18] - [0, 46]
      plain_value [0, 19] - [0, 45]
namespace_statement [1, 0] - [1, 45]
  namespace_name [1, 11] - [1, 13]
  string_value [1, 14] - [1, 44]
rule_set [3, 0] - [3, 8]
  selectors [3, 0] - [3, 3]
    tag_name [3, 0] - [3, 3]
  ERROR [3, 3] - [3, 5]
    ERROR [3, 3] - [3, 5]
  block [3, 6] - [3, 8]
rule_set [5, 0] - [5, 12]
  selectors [5, 0] - [5, 9]
    attribute_selector [5, 0] - [5, 9]
      attribute_name [5, 1] - [5, 3]
      ERROR [5, 3] - [5, 8]
        ERROR [5, 3] - [5, 8]
  block [5, 10] - [5, 12]

tree-sitter / tree-sitter-css

Support namespace selectors #33