Make Alpine app use better Alpine conventions

[markjaquith]

(Great video, by the way)

The Alpine app doesn't actually work right now (you can't use x-for on a <ul> — only on a <template>), and it was coded in not a very Alpine-y way. This PR is a much more idiomatic implementation.

• fixed broken use of x-for on <ul>
• removed unnecessary use of global state
• removed unnecessary function
• move storage syncing to an x-effect
• @submit instead of x-on:submit
• Reset input field after submission
• Formatting cleanup