Increases clickable area of the close btn on modals

[andresgalante]

On alerts we increase the clickable area of the close btns to make them easier to click on devices where the pointer is coarse and improve accessibility.

This PR does 2 things:

1- Introduces the same concept for modals.
1- Changes the align-items to flex-start so the close btn always stays on the upper right corner when the modal-title text wraps.

I am not sure if this should be a global change on _close.scss

What do you think?

[mdo]

Possible to see a quick demo of the before/after by chance?

[andresgalante]

@mdo sure! here is the bug:
https://codepen.io/andresgalante/pen/NvopBJ?editors=1100

• close btn "X" centers instead of been top right
• the x btn click are is smaller than a finger.

Here is the solution:
https://codepen.io/andresgalante/pen/MvLpZw?editors=1100

• The close btn in the top right corner
• the click area is larger

What do you you think?

[patrickhlauke]

Seems fine to me. @mdo ?

[XhmikosR]

LGTM too, but I too wonder if we should change close instead of this specific case. Close seems to be using float currently.