Add note about attachment param

[elanalynn]

Background

In response to a question about the download param not working in button, this PR adds a note about the attachment query param.

This will update these docs.

Solution

Adding the following to the download prop description.

* Use `attachment` query param in URL to force download behavior.
* eg. `to="filename.jpg?attachment"`

🎩

Just a comment; Will generate docs after this PR.

Checklist

• I have 🎩'd these changes
• I have updated relevant documentation

[github-actions]

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