Improvement/Internal: Move to Eleventy v0.7.0

[fpapado]

Eleventy 0.7 supports arbitrary JS templates!

Here's the release notes:
https://github.com/11ty/eleventy/releases/tag/v0.7.0

This is exciting because it allows us to move a bunch of our "semi-shared" templates (i.e. .js files that get re-exported as a shortcodee) into a single, unified "component".
JS templates also suppport async, which can be great for data-fetching somewhere down the tree.

Let's see what the update brings :)