Add props for Download Component

[huytr1995]

Description

Ref: https://github.com/allenai/scholar/issues/31521

Reviewer Instructions

To be able to display the Download button with SVG and no text i passed other two props as icon & classname to help display it as correctly in S2 side

Testing Plan

Manual testing by copypdf-components.js & pdf-components.css into S2 local repo and verify that it will display as intended. Other than that yarn lint:fix & test

Output / Screenshots

[carolinepaulic]

Just a couple minor questions, but overall this looks good :)

[carolinepaulic]

Changes look great! 👍