Add email template page

[FX-Wood]

Solves #112 item 3

This PR allows us to generate email templates for an event page.

Some email clients allow pasting rendered html content from the clipboard, so it's good to have the rendered version of the email on the page. See the below screenshot for an example of what the page looks like. Organizers can copypaste the email contents by starting their selection just below the "copy html" button or use the button to grab the raw html.

[crtr0]

"Copy to HTML" button isn't working

This code <a href="https://getpolaris.ai"><img width="200" alt="undefined logo" src="https://seattlejs.com/_public/images/sponsors/polaris.png" title="undefined logo"></a> should have the sponsor name instead of "undefined".

This code <p>Special thanks to our friends at <a href="URL">undefined</a> for sponsoring snacks for this month's event! 😎</p> should link to the sponsor's website and have their name instead of undefined.

This code <li>📍 LOCATION</li> should have "The Collective" for LOCATION.

This code img width="200" alt="undefined" src="https://seattlejs.com/_public/images/speakers/mike-ryan.jpg" title="Mike Ryan"></p> should have "photo of Mike Ryan" instead of "undefined" for alt.

[FX-Wood]

"Copy to HTML" button isn't working

This code <a href="https://getpolaris.ai"><img width="200" alt="undefined logo" src="https://seattlejs.com/_public/images/sponsors/polaris.png" title="undefined logo"></a> should have the sponsor name instead of "undefined".

This code <p>Special thanks to our friends at <a href="URL">undefined</a> for sponsoring snacks for this month's event! 😎</p> should link to the sponsor's website and have their name instead of undefined.

This code <li>📍 LOCATION</li> should have "The Collective" for LOCATION.

This code img width="200" alt="undefined" src="https://seattlejs.com/_public/images/speakers/mike-ryan.jpg" title="Mike Ryan"></p> should have "photo of Mike Ryan" instead of "undefined" for alt.

These are fixed!