Add props to support aria properties

[Phyks]

• aria-hidden=true is added by default on the icon.
• An ariaLabel prop is available to set an alternate text.

Closes #20

Note: I am not too familiar with writing JS modules, but I guess it should exports everything nicely (css file in particular).

[danawoodman]

Thanks @Phyks! Some notes in the PR before I merge

[danawoodman]

Merged, thanks @Phyks! 🍻

Published in v1.4.0 on npm!

[Phyks]

Thanks!