bug: Comma seperated list of precentages is marked as error in @keyframes

[vivax3794]

Did you check existing issues?

• I have read all the tree-sitter docs if it relates to using the parser
• I have searched the existing issues of tree-sitter-css

Tree-Sitter CLI Version, if relevant (output of tree-sitter --version)

tree-sitter 0.25.1

Describe the bug

Current the grammar expects just one element in keyframe selectors: https://github.com/tree-sitter/tree-sitter-css/blob/master/grammar.js#L89-L92

    keyframe_block: $ => seq(
      choice($.from, $.to, $.integer_value),
      $.block,
    ),

But in fact its valid to provide multiple values.

Steps To Reproduce/Bad Parse Tree

The grammar produces a error on the following input:

@keyframes hello {
    0%, 50% {}
}

(this syntax can also be seen on the MDN keyframes page https://developer.mozilla.org/en-US/docs/Web/CSS/@keyframes#when_properties_are_left_out_of_some_keyframes)

(stylesheet [0, 0] - [3, 0]
  (keyframes_statement [0, 0] - [2, 1]
    (keyframes_name [0, 11] - [0, 16])
    (keyframe_block_list [0, 17] - [2, 1]
      (ERROR [1, 4] - [1, 7]
        (integer_value [1, 4] - [1, 6]
          (unit [1, 5] - [1, 6])))
      (keyframe_block [1, 8] - [1, 14]
        (integer_value [1, 8] - [1, 11]
          (unit [1, 10] - [1, 11]))
        (block [1, 12] - [1, 14])))))

Expected Behavior/Parse Tree

I would expect it to parse correct with the keyframe_block containing multiple integer_value nodes

Repro

@keyframes hello {
    0%, 50% {}
}