Skeleton loader for Releases

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### Description

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a checklist of variations, states, and breakpoints to the description so that reviewers can be sure to cross reference everything that has been completed. -->

In https://gitlab.com/gitlab-org/gitlab/-/issues/201959/ we will introduce an update to the ~"component:skeleton-loader" of the Releases page. This issue adds a variation of the gilab-ui component so that users can be able to see a loading state that always represent Releases in a recognizable way.

- The component variation should be called: `release-card-skeleton-basic`.
- I propose adding the UI to the Product Pages figma file.

### Figma file

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[View branched working file of Component Library →](https://www.figma.com/file/qEddyqCrI7kPSBjGmwkZzQ/branch/EIhkW34nsNcpDXLKQNte4w/Component-library?node-id=2844%3A3)

[(Old) View working file in Figma →](https://www.figma.com/file/9Uee1fu4GrNrEhCHRTi2nK/Release-page-skeleton-load-gitlab-201959?node-id=1%3A2)

### Checklist

Make sure the following are completed before closing the issue:

1. [x] **Assignee**: Design in your working file. When applicable, follow our 
   [structure][structure], [building][building], and [annotation][annotation] guidelines. If you have any questions, reach out to a [FE/UX Foundations designer][foundations-team].
1. [x] **Assignee**: Update the link to the working file in the issue 
   description.
1. [x] **Assignee**: Ask a [FE/UX Foundations designer][foundations-team]
   to review your design (ensure they have edit permissions in Figma).
1. [x] **Reviewer**: Review and approve assignee’s design. Specific design 
   questions can be addressed with comments in Figma. Comment in this issue when the content is less specific to the design or requires greater visibility.
1. [x] **Reviewer**: Assign to a [Figma maintainer][figma-maintainer]
   for final review (make sure they have edit permissions in Figma).
1. [x] **Maintainer**: Review and approve assignee’s changes.
1. [x] **Maintainer**: Add the changes or additions to the target file. For 
   example, you’d copy a final chart design from the working file and paste into the related location in the Data Visualization file.
     1. [x] Ensure that all styles and components now belong to the target file.
     1. [ ] For changes to the **Component Library** file, view the components in the Assets panel to ensure they align with our [asset library structure guidelines][structure].
1. [x] **Maintainer**: When applicable, [publish][publishing] any library 
   changes along with a clear commit message.
1. [-] **Assignee**: Move your working file to the shared Figma project (file was a branch, so archived by the maintainer using the branch feature).
1. [-] **Assignee** (or Maintainer, for community contributions): If it’s a new
   pattern or a significant change, add an agenda item to the next UX weekly call to inform the team.
1. [-] **Assignee**: When applicable, create a merge request in this repository 
   with the [component-guideline template][component-guideline-template]
   to create or update the component’s documentation page. 
1. [-] **Assignee**: When applicable, [create an issue in GitLab UI][new-gitlab-ui-issue] to build or update the component code. Mark the new issue as related to this one.
1. [x] **Assignee**: 🎉 Congrats, you made it! You can now close this issue.

[annotation]: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/blob/master/doc/pajamas-ui-kit.md#adding-descriptions-notes-and-annotations
[building]: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/blob/master/doc/pajamas-ui-kit.md#building-components
[foundations-team]: https://about.gitlab.com/company/team/?department=fe-ux-foundations-team
[figma-maintainer]: https://about.gitlab.com/handbook/engineering/projects/#design.gitlab.com
[publishing]: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/blob/master/doc/pajamas-ui-kit.md#publishing-changes
[structure]: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/blob/master/doc/pajamas-ui-kit.md#structure
[component-guideline-template]: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/blob/master/.gitlab/merge_request_templates/component-guideline.md
[component-archive]: https://www.figma.com/files/project/5472112/Component-archive
[misc-archive]: https://www.figma.com/files/project/10620392/Misc-archive
[new-gitlab-ui-issue]: https://gitlab.com/gitlab-org/gitlab-ui/-/issues/new

Story points: 2.0