edit readme to reference where the current working source is and add screenshots / explanation of what it does

[unusualevent]

So... I initially wanted to give some feedback about the README, and went into the server source code to try to document something, only to find that the master branch has the atom xml feed code commented out... so I was like "wait, where's the source for the app"

anyway, it's only on one of the branches (1.0.1), and would be great if the main branch had it. https://github.com/leafac/kill-the-newsletter/blob/v1.0.1/src/index.ts

based on how that code works, a simple explanation for "how it works" and "how to use it" would be merited. Because "turns email lists into atom feeds" isn't entirely self explanatory without installing it, so I propose the following:

# How It Works
Kill the newsletter! runs its own email server, receiving newsletter notifications for generated email addresses, storing them in Sqlite, and rendering them in atom XML feeds when your favorite feed client requests them.

# How To Use It
See these screenshots:
1. Create a name for a feed
2. Use the email address we provide to paste into the newsletter
3. We'll receive emails on your behalf
4. Use the feed URL we generate, here
5. To view your newsletter lists, go here
6. To delete and unsubscribe from a newsletter, click here

Or something like that. Just really screenshots of the process.

[unusualevent]

e.g. "you will need to run your own email server, you sure about this? just saying the requirements up front..."

[leafac]

Hi @unusualevent,

Thanks for reaching out and for the suggestions.

I recently reworked the documentation. Both in https://kill-the-newsletter.com/ itself, explaining in more detail how things work, as well as the deployment documentation.

Best.