GT-2180 change sorting of language dropdown menu on homepage

[caleballdrin]

Description

https://jira.cru.org/secure/RapidBoard.jspa?rapidView=150&view=detail&selectedIssue=GT-2180
Currently the language menu on the homepage of knowgod.com sorts across the columns going left -> right and then down to the next row.
We'd like to match the way the language menu appears while you're in a tool so that it sorts going down a column, then down the next column, etc.

Changes I made

• Changed flexbox divs to a ul so that it would sort down the column before rows.
• The number of columns changes based on screen size
• Changed CSS to make li items look the same as the divs

[dr-bizz]

I've added one comment about making the modal more center-aligned on larger screens. I know that's not something you did, but it's a easy fix, so wondered if you could throw that into this PR. I added the styles needed on a comment.

[dr-bizz]

Looks great!