Create welcome screen
This screen is similar to the one in Ark, but also shows you a list of recently-opened documents. It looks like this:
| When there are no recent documents | When there are recent documents |
|---|---|
 |
 |
This merge request is a continuation of !422 (closed), which stalled quite close to the finish line. If possible, I'd like to avoid too much bikeshedding, as that's what killed !422 (closed) on the first go-around.