Add directive for use in adding ability to copy permalinks to doc examples

[jaredami]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/mobi/goponents/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

Issue Number: #558

What is the new behavior?

This PR adds a directive which, when added to go-copy element within a go-card-header, enables it to function as a copy-permalink feature for our style-guide.

Example usage:

  <go-card class="go-column go-column--100" id="default">
    <header go-card-header>
      <h2 class="go-heading-2 go-heading--inline">Default</h2>
      <go-copy cardId="default" goCopyDocLink></go-copy>
    </header>
    <div go-card-content>
      <!-- card contend here -->
    </div>
  </go-card>

Does this PR introduce a breaking change?

• Yes
• No

Other information

[eligolding]

I spy an fdescribe

[jaredami]

🤦

[grahamhency]

Looks good to me.