Flyout: use CSS grid to deal with flyout space

[humitos]

In #360 we mentioned we may need to use CSS grid or a similar technique to deal with spacing. Mainly when the flyout is collapsed and the version name is long.

One approach could be to use CSS grid areas: https://ishadeed.com/article/css-grid-area/

We need to talk more about this and explore alternatives (like flexbox, #360 (comment)). Also note that most of this will change when working on the next iteration of the flyout as a "toolbar" or similar: #53