Show a loader on the button while forking

[ValentinH]

This is a follow-up of #1667.

The effect is simple because for now I didn't want to modify the markup of the button.

With my limited CSS skills, I think @CompuIves suggestion regarding nzbin.github.io/three-dots would require to have a div wrapper around the button and a div to display the 3 dots. Do we want to do this?

[ValentinH]

I'll provide another solution by creating a <ProgressButton> component that would wrap the Button itself. It will keep the same API (and pass most props to the Button itself) and support a loading prop (maybe also a success one).
Like this we are not limited and can be creative. Also we are not bloating the default Button component.

[ValentinH]

I have updated the PR to have a better loader. It introduces a <ProgressButton> that wrap the button and add a loader on top of it.

[CompuIves]

I like that! Could you make the dots a bit smaller? That would make the effect a bit more subtle.

[ValentinH]

Do you like this better? I also made it a bit less transparent.

6px was feeling too small to me.

[CompuIves]

Yes, great! Thanks a lot!

[CompuIves]

This implementation is super clean, I love it!

[ValentinH]

I'd love to continue contributing to codesandbox, maybe on something bigger. Do you have a good issue for me?