Add failing test case for shadow DOM selector generation

[niranjan94]

Related to #173

SUMMARY:
✔ 105 tests completed
ℹ 1 test skipped
✖ 2 tests failed

FAILED TESTS:
  Shadow DOM
    ✖ should match shadow element within shadow root
      Chrome Headless 96.0.4664.110 (Mac OS 10.15.7)
    AssertionError: expected ':root > :nth-child(1)' to equal '#shadow-content'
        at Context.<anonymous> (/Users/niranjan/Development/grouped/mockingjay/mockingjay-core/tmp/css-selector-generator/temp/commons.js:12769:46)

    ✖ should match shadow element's child div within shadow root
      Chrome Headless 96.0.4664.110 (Mac OS 10.15.7)
    AssertionError: expected ':root > :nth-child(1) > :nth-child(2)' to equal '#nested-shadow-host'
        at Context.<anonymous> (/Users/niranjan/Development/grouped/mockingjay/mockingjay-core/tmp/css-selector-generator/temp/commons.js:12779:46)