feat(button): add href for Link Variant

[tejas161]

What I did

1. Created new attribute href for pf-button Link.
2. Created new attribute target for pf-button Link.
3. Updated docs for pf-button Link showing examples how to pass an href with target = "_blank" or target = "_self".

Testing Instructions

1. Check if pf-button "link" variant properly redirects to the link passed via href attribute.
2. Check the Accessibility of pf-button Link.

Closes: #2769

[changeset-bot]

🦋 Changeset detected

Latest commit: 1452d1e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@patternfly/elements	Minor

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[github-actions]

✅ Commitlint tests passed!

More Info

{
  "valid": true,
  "errors": [],
  "warnings": [],
  "input": "feat(button): add href for Link Variant"
}

[bennypowers]

@adamjohnson can you take a look at this for usability?

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[zeroedin]

@bennypowers seems like you can click around the href variant and not actually follow the link. The click box for the <a> doesn't appear to cover the whole element clickable area.

[adamjohnson]

If you try to tab to "Link" and "Go to PatternFly" in the Link Variant demo, they get skipped and are not focusable.

It looks like removing tabindex="-1" from the host resolves this issue.