Implement Game Visibility And Add Public Rooms Panel on Front Page

[jimmyfang94]

First pass at: https://github.com/rbtying/shengji/issues/49

• Added a GameVisibility field. Defaults to unlisted, but can be toggled to public. In the future can be used for private games, etc.
• Added a PublicRoomsPane, with functionality to poll a new API that returns all public games and displays them on the first page. Is polled on first render, and then has a refresh button for ad hoc refreshes afterwards.

[jimmyfang94]

thanks for the speedy replies! first time playing with rust, fun learning exp