Refresh the welcome page

[danilo-leal]

TODO:

• Fix width changing when toggling vim mode
• Fix keybindings swapping when changing focus
• Replace "clone repo" with "new file"
• Fix spacing between Vim mode checkbox and theme/keymap icons
• Rewire telemetry so we can see what people are clicking

Release Notes:

• N/A

[mikayla-maki]

Discussed this with @franciskafyi, we're going to take an approach more like VSCode's walkthrough