Added element extensions spec for .matches and .closest ## What does this MR do? Adds tests for `Element.prototype.matches` and `Element.prototype.closest`. ## Are there points in the code the reviewer needs to double check? ## Why was this MR needed? ## Screenshots (if relevant) ## Does this MR meet the acceptance criteria? - [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added - [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md) - [ ] API support added - Tests - [ ] Added for this feature/bug - [ ] All builds are passing - [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html) - [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides) - [ ] Branch has no merge conflicts with `master` (if it does - rebase it please) - [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits) ## What are the relevant issue numbers? See merge request !7755
