fix: correctly parse nested element selectors

[SwetaTanwar]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

What changes did you make? (Give an overview)

Related Issues

Fix #84

Is there anything you'd like reviewers to focus on?

added tests in css repo as well - eslint/css#349

[coveralls]

Pull Request Test Coverage Report for Build 20413711482

Details

• 41 of 41 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.006%) to 98.557%

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Totals
Change from base Build 20089849670:	0.006%
Covered Lines:	11968
Relevant Lines:	12109

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💛 - Coveralls

[snitin315]

LGTM, leaving it open for 2nd review

[nzakas]

Thanks for looking at this. Can you add a test with a comma in the selector?

main {
  p:first-of-type, span {
    margin-top: 0;
  }
}