Update Tutorial Website to new LiveView Native sigil

I also was going through the tutorial building the Cats app to refresh before ElixirConf and ran into a couple issues that can be quick fixed before migrating the tutorial to a LiveBook.

https://liveview-native.github.io/liveview-client-swiftui/tutorials/liveviewnative/01-initial-list/
Section 1
Step 9

LiveView Native sigil ~Z""" with the swiftui modifier
gives
error: undefined function sigil_Z/2

LiveView Native sigil now appears to be ~SWIFTUI""" (and would have to be changed throughout the rest of the tutorial code)

https://liveview-native.github.io/liveview-client-swiftui/tutorials/liveviewnative/01-initial-list/
Section 2
Step 3

Add a new Swift package dependency by selecting File -> Add Packages…, and in the search field, enter https://github.com/liveviewnative/liveview-client-swiftui

should be updated to new liveview-native instead of https://github.com/liveviewnative
https://github.com/liveview-native/liveview-client-swiftui

Those 2 changes at least got me Hello, world! displayed in Xcode.

Open the linked LiveView Native tutorial and review Section 1, Step 9 and Section 2, Step 3 first. Update the sigil references throughout the tutorial and replace the Swift package URL, then verify the Cats app reaches the displayed Hello, world! result in Xcode.