feat: Add pfe-border styles in a separate PR

[castastrophe]

This is actually @eyevana's PR that she graciously merged into my card PR and now I'm pulling it back out so it can be moved through more quickly.

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Link(s) to demo page:

• pfe-card demo page

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For component fixes and features

• Link to issue detailing the request: pfe-card: Add bordered option as a default option #629

What has changed and why

Summarize files edited as part of this MR along with a brief description of what was changed/why.

• Adding a pfe-border attribute to the card component

Testing instructions

Be sure to include detailed instructions on how your update can be tested by another developer.

1. Open the demo page .
2. Check out the first card in the first band on the page which has the pfe-border attribute set on the host.
3. In the inspector, confirm that the border is: 1px solid #d2d2d2 (aka rgb(210, 210, 210))

Browser requirements

Your component should work in all of the following environments:

• Latest 2 versions of Edge
• Internet Explorer 11 (should be useable, not pixel perfect)
• Latest 2 versions of Firefox (one on Mac OS, one of Windows OS)
• Firefox 60.7.2 (or latest version for Red Hat Enterprise Linux distribution)
• Latest 2 versions of Chrome (one on Mac OS, one of Windows OS)
• Latest 2 versions of Safari
• Galaxy S9 Firefox
• iPhone X Safari
• iPad Pro Safari
• Pixel 3 Chrome

Ready-for-merge Checklist

Check off items as they are completed. Feel free to delete items if they are not applicable to your PR.

• Expected files: all files in this pull request are related to one request or issue (no stragglers or scope-creep).
• Tests have been updated to cover these changes.
• Browser testing passed.
• Documentation (README.md, WHY.md, etc.) updated or added.
• Link to the demo recording
• Approved by designer.

Be sure to share your updates with the patternfly-elements-contribute@redhat.com mailing list!

[starryeyez024]

Lather Germs, To Mitigate.

Confirmed that the pfe-border attribute works, and the 3 border variables also work 👍

--pfe-card--BorderWidth: 5px;
--pfe-card--BorderColor: pink;
--pfe-card--BorderStyle: dashed;