Option to select default landing page in new layout.

### Your use case

#### What would you like to do?

When Element opens with the new layout turned on, I would like to be greeted with the "Favorites" tab of chats instead of "All chats"

#### Why would you like to do it?

I would like to do so as it is convenient, not everyone wants to see every 6000+ messages when they go and launch Element cluttered everywhere. I would like to see only my favorite chats when I open Element.

#### How would you like to achieve it?

Just add a selection box to select a default landing page in the settings menu. Those who want "All chats" can remain in "All chats" and those who want another landing page can select that one (like Favorites, for instance) instead.

### Have you considered any alternatives?

Using the old layout until the new one implements this feature or a similar one. Using another client if this feature is left in the dust.

### Additional context

I believe for people to eventually use and accept the new layout, options like these are important.

### Are you willing to provide a PR?

No