Make sidebar useful

The current sidebar is quite useless, Edge has a really useful sidebar that Brave can learn a lot from, side-by-side apps and messenger integrations are just a few things. Leo works great but it is currently the only reason to have the sidebar active. On a side note, Leo could use a button on the top bar (near the extensions and hamburger menu) for people who don’t like the sidebar but would like to use Leo more frequently.