feat(Button): add close icon support (reactstrap/reactstrap#1182)

[median-man]

This PR addresses #1182.

Add support for close icon utility from Bootstrap 4.
This commit adds an optional boolean property, 'close', to the
Button component. Applying the close prop will render the Close
icon utility from Bootstrap 4.

Update documentation on the Button component to demonstrate usage
of the close prop.

• Bug fix
• New feature
• Chore
• Breaking change
• There is an open issue which this change addresses
• I have read the CONTRIBUTING document.
• My commits follow the Git Commit Guidelines
• My code follows the code style of this project.
• My change requires a change to the documentation.
• • I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

This is my first time submitting a PR. I welcome any constructive feedback you have to offer if you are reviewing this PR.

Closes #1182

[TheSharpieOne]

Sorry for the delay, but what do you think about defaulting children to <span aria-hidden>&times;</span> when close is true? That way people would be able to do <Button close /> to get what is probably the most common usages which includes ×. Providing children would of course show the children instead.

[median-man]

I think that is a great idea! I'll update the pr shortly.

Sorry for the delay, but what do you think about defaulting children to <span aria-hidden>&times;</span> when close is true? That way people would be able to do <Button close /> to get what is probably the most common usages which includes ×. Providing children would of course show the children instead.

[median-man]

Pending checks, I've added the default children to the commit. If anything else needs fixing, I would be happy to see to it tomorrow. @TheSharpieOne

[TheSharpieOne]

Thanks for the PR!