Update Eleventy (2.0) and other dependencies

Thanks to assistance from @lud, @ryanccn, and @geshan, it was determi…

…ned that build-speed could be improved with a small adjustment.

This builds Tailwind _after_ eleventy:build is done. Thank you, @geshan!

Set the default template engine to njk

Minor bugfix (see desc), polish, version bump

{{ content | safe }} has been updated to {{ content }} in base.html. Eleventy (or, perhaps Nunjucks?) threw an error and I couldn't find anything online explaining *why*, so removing it seemed like the next best option. 🤞

Bump @11ty/eleventy from 0.12.1 to 1.0.0

Bumps [@11ty/eleventy](https://github.com/11ty/eleventy) from 0.12.1 to 1.0.0.
- [Release notes](https://github.com/11ty/eleventy/releases)
- [Changelog](https://github.com/11ty/eleventy/blob/master/docs/meta-release.md)
- [Commits](11ty/eleventy@v0.12.1...v1.0.0)

---
updated-dependencies:
- dependency-name: "@11ty/eleventy"
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

If you want to upgrade your project from Tailwind CSS v2.x to v3.x, t…

…he Tailwind folks have a _wonderful_ [Upgrade Guide](https://tailwindcss.com/docs/upgrade-guide) you should review.

See commit message

I'm bad at git — reapplying changes that I missed

This bumps autoprefixer and adds a .nvmrc file for Netlify