add top and bottom for vertical-align

[qayshp]

I did not see a contribution guide in this repository, so please let me know if I'm missing something or you would prefer different styles.

I opened #161 regarding this. Discussion can be there or here.

I am trying to set vertical alignment for non-text items in one of my styles, and while there are both workarounds as well as other ways to do this, I would like to have parity with the CSS standard on this.

These two values are listed on MDN: vertical-align, and in the CSS level 1 and level 2 W3C specs.

vertical-align: top;
vertical-align: bottom;

[mathieuleclaire]

Sounds good to me

[qayshp]

Thanks!